
2 
Paper

Making Inferences from 2x2 Tables: The Inadequacy of the Fisher Exact\r\nTest for Observational Data and a Principled Bayesian Alternative
Sekhon, Jasjeet

Uploaded 
08172005

Keywords 
Fisher exact test randomization inference permutation
tests Bayesian tests difference of proportions observational data

Abstract 
The Fisher exact test is the dominant method of making inferences from
2x2 tables where the number of observations is small. Although the
Fisher test and approximations to it are used in a large number of
studies, these tests rest on a data generating process which is
inappropriate for most applications for which they are used. The
canonical Fisher test assumes that both of the margins in a 2x2 table
are fixed by constructioni.e., both the treatment and outcome
margins are fixed a priori. If the data were generated by an
alternative process, such as binomial, negative binomial or Poisson
binomial sampling, the Fisher exact test and approximations to it do
not have correct coverage. A Bayesian method is offered which has
correct coverage, is powerful, is consistent with a binomial process
and can be extended easily to other distributions. A prominent 2x2
table which has been used in the literature by Geddes (1990) and
Sekhon (2004) to explore the relationship between foreign threat and
social revolution (Skocpol, 1979) is reanalyzed. The Bayesian method
finds a significant relationship even though the Fisher and related
tests do not. A Monte Carlo sampling experiment is provided which
shows that the Bayesian method dominates the usual alternatives in
terms of both test coverage and power when the data are generated by a
binomial process. 

3 
Paper

Why we (usually) don't have to worry about multiple comparisons
Gelman, Andrew
Hill, Jennifer
Yajima, Masanao

Uploaded 
06012008

Keywords 
Bayesian inference hierarchical modeling multiple comparisons type S error statistical significance

Abstract 
The problem of multiple comparisons can disappear when viewed from a Bayesian perspective. We propose building multilevel models in the settings where multiple comparisons arise. These address the multiple comparisons problem and also yield more efficient estimates, especially in settings with low grouplevel variation, which is where multiple comparisons are a particular concern.
Multilevel models perform partial pooling (shifting estimates toward each other), whereas classical procedures typically keep the centers of intervals stationary, adjusting
for multiple comparisons by making the intervals wider (or, equivalently, adjusting the pvalues corresponding to intervals of fixed width). Multilevel estimates make comparisons more conservative, in the sense that intervals for comparisons are more likely to include zero; as a result, those comparisons that are made with confidence are more likely to be valid. 

4 
Paper

A Statistical Method for Empirical Testing of Competing Theories
Imai, Kosuke
Tingley, Dustin

Uploaded 
08242010

Keywords 
EITM finite mixture model Bayesian statistics multiple testing false discovery rate EM algorithm

Abstract 
Empirical testing of competing theories lies at the heart of social science research. We demonstrate that a very general and wellknown class of statistical models, called finite mixture models, provides an effective way of rival theory testing. In the proposed framework, each observation is assumed to be generated from a statistical model implied by one of the theories under consideration. Researchers can then estimate the probability that a specific observation is consistent with either of the competing theories. By directly modeling this probability with the characteristics of observations, one can also determine the conditions under which a particular theory applies. We discuss a principled way to identify a list of observations that are statistically significantly consistent with each theory. Finally, we propose several measures of the overall performance of a particular theory. We illustrate the advantages of our method by applying it to an influential study on trade policy preferences. 

5 
Paper

The Insignificance of Null Hypothesis Significance Testing
Gill, Jeff

Uploaded 
02061999

Keywords 
hypothesis testing inverse probability Fisher NeymanPearson Bayesian approaches confidence sets metaanalysis

Abstract 
The current method of hypothesis testing in the social sciences is under intense criticism
yet most political scientists are unaware of the important issues being
raised. Criticisms focus on the construction and interpretation of a
procedure that has dominated the reporting of empirical results for over fifty years.
There is evidence that null hypothesis significance testing as practiced in political
science is deeply flawed and widely misunderstood. This is important since most
empirical work in political science argues the value of findings through the use of
the null hypothesis significance test.
In this article I review the history of the null hypothesis significance
testing paradigm in the social sciences and discuss major problems, some of which
are logical inconsistencies while others are more interpretive in nature. I suggest
alternative techniques to convey effectively the importance of dataanalytic findings.
These recommendations are illustrated with examples using empirical
political science publications. 

6 
Paper

Identifying IntraParty Voting Blocs in the UK House of Commons
Quinn, Kevin
Spirling, Arthur

Uploaded 
07192005

Keywords 
rollcall analysis UK House of Commons Bayesian nonparametrics Dirichlet process mixtures

Abstract 
Legislative voting records are an important source of information about
legislator preferences, intraparty cohesiveness, and the divisiveness
of various policy issues. Standard methods of analyzing a legislative
voting record tend to have serious drawbacks when applied to
legislatures, such as the UK House of Commons, that feature highly
disciplined parties, strategic voting, and large amounts of missing
data. We present a method (based on a Dirichlet process mixture model)
for analyzing such voting records that does not suffer from these same
problems. We apply the method to the voting records of Labour and
Conservative Party MPs in the 19972001 session of the UK House of
Commons. Our method has a number of advantages over existing approaches.
It is modelbased and thus allows one to make probability statements
about quantities of interest. It allows one to estimate the number of
voting blocs within a party or any other group of MPs. It handles
missing data in a principled fashion and does not rely on an ad hoc
distance metric between voting profiles. Finally, it can be used as both
a predictive model and an exploratory model. We illustrate these points
in our analysis of the UK data. 

9 
Paper

Estimation and Inference by Bayesian Simulation: an online resource for social scientists
Jackman, Simon

Uploaded 
08301999

Keywords 
Markov chain Monte Carlo Bayesian statistics howto BUGS ordinal probit time series

Abstract 
http://tamarama.stanford.edu/mcmc
a Webbased online resource for Markov chain Monte Carlo,
specifically tailored for social scientists.
MCMC is probably the most exciting development in statistics in the
last ten years. But to date, most applications of MCMC methods are in
biostatistics, making it difficult for social scientists to fully
grasp the power of MCMC methods. In providing this online resource I
aim to overcome this deficiency, helping to put MCMC in the reach of
social scientists.
The resource comprises:
(*) a set of worked examples
(*) data and programs
(*) links to other relevant web sites
(*) notes and papers
At the meetings in Atlanta, I will present two of the worked examples,
which are part of this document:
(*) Cosponsor: computing auxiliary quantities from MCMC output (e.g.,
percent correctly predicted in a logit/probit model of legislative
behavior; cf Herron 1999).
(*) Delegation: estimating a timeseries model for ordinal data
(e.g., changes to the U.S. president's discretionary power in trade
policy, 18901990; cf Epstein and O'Halloran 1996). 

10 
Paper

Democracy as a Latent Variable
Treier, Shawn
Jackman, Simon

Uploaded 
07162003

Keywords 
democracy Polity measurement latent variables Bayesian statistics itemresponse model ordinal data latent class analysis democratic peace Markov chain Monte Carlo

Abstract 
Measurement is critical to the social scientific enterprise. Many key concepts in socialscientific theories are not observed
directly, and researchers rely on assumptions (tacitly or explicitly, via formal measurement models) to operationalize these concepts in empirical work. In this paper we apply formal, statistical measurement models to the Polity indicators of democracy and autocracy, used widely in studies of international relations. In so doing, we make explicit the hitherto implicit assumptions underlying scales built
using the Polity indicators. We discuss two models: one in which democracy is operationalized as a latent continuous variable, and another in which democracy is operationalized as a latent class. Our modeling approaches allow us to assess the measurement error in the resulting measure of democracy. We show that this measurement error is considerable, and has substantive
consequences when using a measure of democracy as an independent variable in crossnational statistical analysis. Our analysis suggests that skepticism as to the precision of the Polity democracy scale is wellfounded, and that many researchers have been overly sanguine about the properties of the Polity democracy scale in applied statistical work. 

11 
Paper

Nonparametric Priors For Ordinal Bayesian Social Science Models: Specification and Estimation
Gill, Jeff
Casella, George

Uploaded 
08212008

Keywords 
generalized linear mixed model ordered probit Bayesian approaches nonparametric priors Dirichlet process mixture models nonparametric Bayesian inference

Abstract 
A generalized linear mixed model, ordered probit, is used to estimate levels of stress in presidential political appointees as a means of understanding their surprisingly short tenures. A Bayesian approach is developed, where the random effects are modeled with a Dirichlet process mixture prior, allowing for useful incorporation of prior information, but retaining some vagueness in the form of the prior. Applications of Bayesian models in the social sciences are typically done with ``noninformative'' priors, although some use of informed versions exists. There has been disagreement over this, and our approach may be a step in the direction of satisfying both camps. We give a detailed description of the data, show how to implement the model, and describe some interesting conclusions. The model utilizing a nonparametric prior fits better and reveals more information in the data than standard approaches. 

12 
Paper

Modeling Electoral Coordination: Voters, Parties and Legislative Lists in Uruguay
Levin, Ines
Katz, Gabriel

Uploaded 
04202011

Keywords 
electoral coordination number of parties Bayesian estimation multilevel modeling strategic voting

Abstract 
During each electoral period, the strategic interaction between voters and political elites determines the number of viable candidates in a district. In this paper, we implement a hierarchical seemingly unrelated regression model to explain electoral coordination at the district level in Uruguay as a function of district magnitude, previous electoral outcomes and electoral regime. Elections in this country are particularly useful to test for institutional effects on the coordination process due to the large variations in district magnitude, to the simultaneity of presidential and legislative races held under different rules, and to the reforms implemented during the period under consideration. We find that district magnitude and electoral history heuristics have substantial effects on the number of competing and votedfor parties and lists. Our modeling approach uncovers important interactioneffects between the demand and supply side of the political market that were often overlooked in previous research. 

14 
Paper

Candidate Viability and Voter Learning in the Presidential Nomination Process
Paolino, Philip

Uploaded 
08301999

Keywords 
beta distribution maximum likelihood heterogeneity Bayesian

Abstract 
Candidates' viability and momentum are important features of the
presidential nomination process in the United States, and much work
has examined how both influence the outcome of the nomination campaign
(e.g. Aldrich 1980a, Aldrich 1980b, Bartels 1988, Brady and Johnston
1987) Previous treatments, however, have focused upon candidates'
expectations of winning or losing the nomination. A critical feature
that has been mentioned, but not addressed directly is the volatility
of these expectations. In this paper, I use a view of viability and
momentum that considers both expectations and the variance of the
public's perceptions about candidates' viability which allows us to
examine how voters use new information to update their beliefs about
both elements of candidates' viability and provides a basis for
assessing candidates' potential momentum. 

17 
Paper

Bayesian Measures of Explained Variance and Pooling in Multilevel (Hierarchical) Models
Gelman, Andrew
Pardoe, Iain

Uploaded 
04162004

Keywords 
adjusted Rsquared Bayesian inference hierarchical model multilevel regression partial pooling shrinkage

Abstract 
Explained variance (R2) is a familiar summary of the fit of a linear
regression and has been generalized in various ways to multilevel
(hierarchical) models. The multilevel models we consider in this paper
are characterized by hierarchical data structures in which individuals
are grouped into units (which themselves might be further grouped into
larger units), and there are variables measured on individuals and each
grouping unit. The models are based on regression relationships at
different levels, with the first level corresponding to the individual
data, and subsequent levels corresponding to betweengroup regressions
of individual predictor effects on grouping unit variables. We present
an approach to defining R2 at each level of the multilevel model, rather
than attempting to create a single summary measure of fit. Our method is
based on comparing variances in a single fitted model rather than
comparing to a null model. In simple regression, our measure generalizes
the classical adjusted R2. We also discuss a related variance comparison
to summarize the degree to which estimates at each level of the model
are pooled together based on the levelspecific regression relationship,
rather than estimated separately. This pooling factor is related to the
concept of shrinkage in simple hierarchical models. We illustrate the
methods on a dataset of radon in houses within counties using a series
of models ranging from a simple linear regression model to a multilevel
varyingintercept, varyingslope model.


18 
Paper

Operationalizing and Testing Spatial Theories of Voting
Quinn, Kevin M.
Martin, Andrew D.

Uploaded 
04151998

Keywords 
spatial voting factor analysis multinomial probit multinomial logit Bayesian inference model comparison Bayes factors MCMC Dutch politics Danish politics

Abstract 
Spatial models of voting behavior provide the foundation for a
substantial number of theoretical results. Nonetheless, empirical
work involving the spatial model faces a number of potential
difficulties. First, measures of the latent voter and candidate issue
positions must be obtained. Second, evaluating the fit of competing
statistical models of voter choice is often more complicated than
previously realized. In this paper, we discuss precisely these
issues. We argue that confirmatory factor analysis applied to
masslevel issue preference questions is an attractive means of
measuring voter ideal points. We also show how party issue positions
can be recovered using a variation of this strategy. We go on to
discuss the problems of assessing the fit of competing statistical
models (multinomial logit vs. multinomial probit) and competing
explanations (those based on spatial theory vs. those derived from
other theories of voting such as sociological theories). We
demonstrate how the Bayesian perspective not only provides
computational advantages in the case of fitting the multinomial probit
model, but also how it facilitates both types of comparison mentioned
above. Results from the Netherlands and Denmark suggest that even
when the computational cost of multinomial probit is disregarded, the
decision whether to use multinomial probit (MNP) or multinomial logit
(MNL) is not clearcut. 

19 
Paper

Estimating Incumbency Advantage and Campaign Spending Effect without the Simultaneity Bias
Fukumoto, Kentaro

Uploaded 
07162006

Keywords 
Incumbency Advantage Campaign Spending Simultaneity Bias Bayesian Nash equilibria normal vote

Abstract 
In estimating incumbency advantage and campaign spending effect, simultaneity problem is composed of stochastic dependence and parametric dependence. Scholars have tried to solve the former, while the present paper intends to tackle the latter. Its core idea is to estimate parameters by maximizing likelihood of all endogenous variables (vote, both parties' candidate qualities and campaign spending) simultaneously. In order to do it, I take advantage of theories of electoral politics rigorously, model each endogenous variables by the others (or their expectation), derive Bayesian Nash equilibria, and plug them into my estimator. I show superiority of my model compared to the conventional estimators by Monte Carlo simulation. Empirical application of this model to the recent U.S. House election data demonstrates that incumbency advantage is smaller than previously shown and that entry of incumbent and strong challenger is motivated by electoral prospect. 

20 
Paper

Bayesian Combination of State Polls and Election Forecasts
Lock, Kari
Gelman, Andrew

Uploaded 
09212008

Keywords 
election prediction preelection polls Bayesian updating shrinkage estimation

Abstract 
In February of 2008, SurveyUSA polled 600 people in each state and asked who they would vote for in either headtohead matchup: Obama vs. McCain, and Clinton vs. McCain. Here we integrate these polls with prior information; how each state voted in comparison to the national outcome in the 2004 election. We use Bayesian methods to merge prior and poll data, weighting each by its respective information. The variance for our poll data incorporates both sampling variability and variability due to time before the election, estimated using preelection poll data from the 2000 and 2004 elections. The variance for our prior data is estimated using the results of the past nine presidential elections. The union of prior and poll data results in a posterior distribution predicting how each state will vote, in turn giving us posterior intervals for both the popular and electoral vote outcomes of the 2008 presidential election. Lastly, these posterior distributions are updated with the most recent poll data as of August, 2008. 

21 
Paper

Practical Issues in Implementing and Understanding Bayesian Ideal Point Estimation
Bafumi, Joseph
Gelman, Andrew
Park, David K.
Kaplan, Noah

Uploaded 
06112004

Keywords 
Ideal points Bayesian Logistic regression Rasch model

Abstract 
In recent years, logistic regression (Rasch) models have been
used in political science for estimating ideal points of
legislators and Supreme Court justices. These models present
estimation and identifiability challenges, such as improper
variance estimates, scale and translation invariance, reflection
invariance, and issues with outliers. We resolve these issues
using Bayesian hierarchical modeling, linear transformations,
informative regression predictors, and explicit modeling for
outliers. In addition, we explore new ways to usefully display
inferences and check model fit.


22 
Paper

A Random Effects Approach to Legislative Ideal Point Estimation
Bailey, Michael

Uploaded 
04211998

Keywords 
ideal points random effects models Bayesian estimation em algorithm

Abstract 
Conventionally, scholars use either standard probit/logit techniques or
fixedeffect methods to estimate legislative ideal points. However,
these methods are unsatisfactory when a limited number of votes are
available: standard probit/logit methods are poorly equipped to handle
multiple votes and fixedeffect models disregard serious ``incidental
parameter'' problems. In this paper I present an alternative approach
that moves beyond singlevote probit/logit analysis without requiring the
large number of votes needed for fixedeffects models. The method is
based on a random effects, panel logit framework that models ideal points
as stochastic functions of legislator characteristics. Monte Carlo
results and an application to trade politics demonstrate the practical
usefulness of the method. 

23 
Paper

An Automated Method of TopicCoding Legislative Speech Over Time with Application to the 105th108th U.S. Senate
Quinn, Kevin
Monroe, Burt
Colaresi, Michael
Crespin, Michael
Radev, Dragomir

Uploaded 
07182006

Keywords 
legislatures agendas content analysis Bayesian time series cluster analysis unsupervised learning

Abstract 
We describe a method for statistical learning from speech documents that we apply to the Congressional Record in order to gain new insight into the dynamics of the political agenda. Prior efforts to evaluate the attention of elected representatives across topic areas have largely been expensive manual coding exercises and are generally circumscribed along one or more features of detail: limited time periods, high levels of temporal aggregation, and coarse topical categories. Conversely, the Congressional Record has scarcely been used for such analyses, largely because it contains too much information to absorb manually. We describe here a method for
inferring, through the patterns of word choice in each speech and the dynamics of word choice patterns across time, (a) what the topics of speeches are, and (b) the probability that attention will be paid to any given topic or set of topics over time. We use the model to examine the agenda in the United States Senate from 19972004, based on a new database of over 70 thousand speech documents containing over 70 million words. We estimate the model for 42 topics and provide evidence that we can reveal speech topics that are both distinctive and interrelated in substantively meaningful ways. We demonstrate further that the dynamics our model gives us leverage into important questions about the dynamics of the political agenda. 

25 
Paper

Estimating incumbency advantage and its variation, as an example of a before/after study
Gelman, Andrew
Huang, Zaiying

Uploaded 
02072003

Keywords 
Bayesian inference beforeafter study Congressional elections Gibbs

Abstract 
Incumbency advantage is one of the most studied features in American
legislative elections. In this paper, we construct and implement an
estimate that allows incumbency advantage to vary between individual
incumbents. This model predicts that openseat elections will be less
variable than those with incumbents running, an observed empirical
pattern that is not explained by previous models. We apply our method
to the U.S. House of Representatives in the twentieth century: our
estimate of the overall pattern of incumbency advantage over time is
similar to previous estimates (although slightly lower), and we also
find a pattern of increasing variation. In addition to the
application to incumbency advantage, our approach represents a new
method, using multilevel modeling, for estimating effects in
before/after studies. 

27 
Paper

Presidential Approval: the case of George W. Bush
Beck, Nathaniel
Jackman, Simon
Rosenthal, Howard

Uploaded 
07192006

Keywords 
presidential approval public opinion polls house effects dynamic linear model Bayesian statistics Markov chain Monte Carlo state space pages of killer graphs

Abstract 
We use a Bayesian dynamic linear model to track approval for George W. Bush over time. Our analysis deals with several issues that have been usually addressed separately in the extant literature. First, our analysis uses polling data collected at a higher frequency than is typical, using over 1,100 published national polls, and data on macroeconomic conditions collected at the weekly level. By combining this much poll information, we are much better poised to examine the public's reactions to events over shorter time scales than can the typical analysis of approval that utilizes monthly or quarterly approval. Second, our statistical modeling explicitly deals with the sampling error of these polls, as well as the possibility of bias in the polls due to house effects. Indeed, quite aside from the question of ``what drives approval?'', there is considerable interest in the extent to which polling organizations systematically diverge from one another in assessing approval for the president. These bias parameters are not only necessary parts of any realistic model of approval that utilizes data from multiple polling organizations, but easily estimated via the Bayesian dynamics linear model. 

28 
Paper

Spike and Slab Prior Distributions for Simultaneous Bayesian Hypothesis Testing, Model Selection, and Prediction, of Nonlinear Outcomes
Pang, Xun
Gill, Jeff

Uploaded 
07132009

Keywords 
Spike and Slab Prior Hypothesis Testing Bayesian Model Selection Bayesian Model Averaging Adaptive Rejection Sampling Generalized Linear Model

Abstract 
A small body of literature has used the spike and slab prior specification for model selection with strictly linear outcomes. In this setup a twocomponent mixture distribution is stipulated for coefficients of interest with one part centered at zero with very high precision (the spike) and the other as a distribution diffusely centered at the research hypothesis (the slab). With the selective shrinkage, this setup incorporates the zero coefficient contingency directly into the modeling process to produce posterior probabilities for hypothesized outcomes. We extend the model to qualitative responses by designing a hierarchy of forms over both the parameter and model spaces to achieve variable selection, model averaging, and individual coefficient hypothesis testing. To overcome the technical challenges in estimating the marginal posterior distributions possibly with a dramatic ratio of density heights of the spike to the slab, we develop a hybrid Gibbs sampling algorithm using an adaptive rejection approach for various discrete outcome models, including dichotomous, polychotomous, and count responses. The performance of the models and methods are assessed with both Monte Carlo experiments and empirical applications in political science. 

30 
Paper

The Problem with Quantitative Studies of International Conflict
Beck, Nathaniel
King, Gary
Zeng, Langche

Uploaded 
07151998

Keywords 
Conflict logit neural networks forecasting Bayesian analysis

Abstract 
Despite immense data collections, prestigious journals, and
sophisticated analyses, empirical findings in the literature on
international conflict are frequently unsatisfying. Statistical
results appear to change from article to article and specification
to specification. Very few relationships hold up to replication
with even minor respecification. Accurate forecasts are
nonexistent. We provide a simple conjecture about what accounts for
this problem, and offer a statistical framework that better matches
the substantive issues and types of data in this field. Our model,
a version of a ``neural network'' model, forecasts substantially
better than any previous effort, and appears to uncover some
structural features of international conflict. 

31 
Paper

Expressive Bayesian Voters, their Turnout Decisions, and Double Probit
Achen, Christopher

Uploaded 
07172006

Keywords 
turnout expressive Bayesian probit scobit EITM

Abstract 
Voting is an expressive act. Since people are not born wanting to express themselves politically, the desire to vote must be acquired, either by learning about the candidates, by using party identification as a cognitive shortcut, or by contact from a trusted source. Modeled as Bayesian updating, this simple explanatory framework has dramatic implications for the understanding of voter turnout. It mathematically implies the main empirical generalizations familiar from the literature, it predicts hitherto unnoticed patterns that appear in turnout data, it provides a better fitting statistical model (double probit) for sample surveys of turnout, and it allows researchers to forecast turnout patterns in new elections when circumstances change. Thus the case is strengthened for the Bayesian voter model as a central organizing principle for public opinion and voting behavior. 

32 
Paper

Joint Modeling of Dynamic and CrossSectional Heterogeneity: Introducing Hidden Markov Panel Models
Park, Jong Hee

Uploaded 
07142009

Keywords 
Bayesian statistics Fixedeffects Hidden Markov models Markov chain Monte Carlo methods Randomeffects Reversible jump Markov chain Monte Carlo

Abstract 
Researchers working with panel data sets often face situations where changes in unobserved factors have produced changes in the crosssectional heterogeneity across time periods. Unfortunately, conventional statistical methods for panel data are based on the assumption that the unobserved crosssectional heterogeneity is time constant. In this paper, I introduce statistical methods to diagnose and model changes in the unobserved heterogeneity. First, I develop three combinations of a hidden Markov model with panel data models using the Bayesian framework; (1) a baseline hidden Markov panel model with varying fixed effects and varying random effects; (2) a hidden Markov panel model with varying fixed effects; and (3) a hidden Markov panel model with varying intercepts. Second, I present model selection methods to diagnose the dynamic heterogeneity using the marginal likelihood method and the reversible jump Markov chain Monte Carlo method. I illustrate the utility of these methods using two important ongoing political economy debates; the relationship between income inequality and economic growth and the effect of institutions on income inequality. 

33 
Paper

Unresponsive, Unpersuaded: The Unintended Consequences of Voter Persuasion Efforts
Bailey, Michael
Hopkins, Daniel
Rogers, Todd

Uploaded 
08092013

Keywords 
causal inference field experiments persuasion attrition multiple imputation Approximate Bayesian Bootstrap

Abstract 
Can randomized experiments at the individual level help assess the persuasive effects of campaign tactics? In the contemporary U.S., vote choice is not observable, so one promising research design to assess persuasion involves randomizing appeals and then using a survey to measure vote intentions. Here, we analyze one such field experiment conducted during the 2008 presidential election in which 56,000 registered voters were assigned to persuasion in person, by phone, and/or by mail. Persuasive appeals by canvassers had two unintended consequences. First, they reduced responsiveness to the followup survey, lowering the response rate sharply among infrequent voters. Second, various statistical methods to address the resulting biases converge on a counterintuitive conclusion: the persuasive canvassing reduced candidate support. Our results allow us to rule out even small effects in the intended direction, and illustrate the backlash that persuasion can engender. 

34 
Paper

Connecting Interest Groups and Congress: A New Approach to Understanding Interest Group Success
Victor, Jennifer Nicoll

Uploaded 
07162002

Keywords 
Interest Groups Congress Multiple Imputation Bayesian Information Criterion Ordinal Probit Nonnested Models Legislative Context

Abstract 
The primary challenge in explaining interest group legislative success in
Congress has been methodological. The discipline requires at least two
critical elements to make progress on this important question. First, we
need a theory that accounts for the highly interactive spatial game
between interest groups and legislators. Second, the discipline needs an
empirical model that associates interest groups and their activities with
specific congressional bills.
In this project I begin to contribute to our understanding of the complex
relationship between interest groups and Congress. I develop a theory of
group success that is based upon the strategies in which groups engage,
the groups' organizational capacity, and the strategic context of
legislation. I predict that groups will tailor their activities (and
strategically spend their resources) in Congress based upon two critical
factors: whether the group supports or opposes the legislation, and the
legislative environment for the bill.
To test this model I develop a unique sampling procedure and survey
design. I use legislative hearings to generate a sample of groups that
are associated with specific issues and survey them about their activities
on those issues. Then, I associate each group's issue with a specific
bill in Congress. I then track the bill to discern its final status. I
create a dependent variable of interest group success that is based on the
group's position (favor or oppose) and the final status of the bill. This
sampling procedure and dependent variable allow me to make inferences
about group behavior over specific legislative proposals. I develop
independent variables of group activity, group organizational capacity,
and legislative context from the survey instrument and objective
information about the bills.
To fill in gaps in the survey data set, I use a multiple imputation method
that generates plausible values based on given distributions of data. I
estimate two modelsone for groups in favor of legislation, and one for
opposition groups. The ordinal probit models generally support the
theoretical expectations. In sum, I find that groups can best expend
their resources in pursuit of rules that advantage their position rather
than fighting for bill content. 

35 
Paper

Pooling Disparate Observations
Bartels, Larry M.

Uploaded 
01011995

Keywords 
induction statistical inference Bayesian statistics econometrics observations Ftest pooling fractional pooling

Abstract 
Data analysts frequently face difficult choices about whether
to pool disparate observations in their statistical analyses.
I explore the inferential ramifications of such choices, and
propose a new technique, dubbed "fractional pooling," which
provides a simple way to incorporate prior beliefs about the
theoretical relevance of disparate observations. The technique
is easy to implement and has a plausible rationale in Bayesian
statistical theory. I illustrate the potential utility of
fractional pooling by applying the technique to political data
originally analyzed by Ashenfelter (1994), Powell (1982), and
Alesina et al. (1993). These examples demonstrate that
conventional approaches to analyzing disparate observations can
be seriously misleading, and that the approach proposed here can
enrich our understanding of the inferential implications of
unavoidably subjective judgments about the theoretical relevance
of available data. 

36 
Paper

Designing and Analyzing Randomized Experiments
Horiuchi, Yusaku
Imai, Kosuke
Taniguchi, Naoko

Uploaded 
07052005

Keywords 
Bayesian inference causal inference noncompliance nonresponse randomized block design

Abstract 
In this paper, we demonstrate how to effectively design and analyze randomized experiments, which are becoming increasingly common in political science research. Randomized experiments provide researchers with an opportunity to obtain unbiased estimates of causal effects because the randomization of treatment guarantees that the treatment and control groups are on average equal in both observed and unobserved characteristics. Even in randomized experiments, however, complications can arise. In political science experiments, researchers often cannot force subjects to comply with treatment assignment or to provide the information necessary for the estimation of causal effects. Building on the recent statistical literature, we show how to make statistical adjustments for these noncompliance and nonresponse problems when analyzing randomized experiments. We also demonstrate how to design randomized experiments so that the potential impact of such complications is minimized. 

37 
Paper

Balancing Competing Demands: PositionTaking and Election Proximity in the European Parliament
Lindstaedt, Rene
Slapin, Jonathan
Vander Wielen, Ryan

Uploaded 
07312009

Keywords 
Legislative Politics European Parliament Comparative Politics Bayesian IRT Parties Formal Theory

Abstract 
Parties value unity, yet, members of parliament face competing demands, giving them incentives to deviate from the party. For members of the European Parliament (MEPs), these competing demands are national party and European party group pressures. Here, we look at how MEPs respond to those competing demands. We examine ideological shifts within a single parliamentary term to assess how European Parliament (EP) election proximity affects party group cohesion. Our formal model of legislative behavior with multiple principals yields the following hypothesis: When EP elections are proximate, national party delegations shift toward national party positions, thus weakening EP party group cohesion. For our empirical test, we analyze roll call data from the fifth EP (19992004) using Bayesian item response models. We find significant movement among national party delegations as EP elections approach, which is consistent with our theoretical model, but surprising given the existing literature on EP elections as secondorder contests. 

38 
Paper

StateLevel Opinions from National Surveys: Poststratification using Hierarchical Logistic Regression
Park, David K.
Gelman, Andrew
Bafumi, Joseph

Uploaded 
07122002

Keywords 
Bayesian Inference Hierarchical Logit Poststratification Public Opinion States Elections

Abstract 
Previous researchers have pooled national surveys in order to construct
statelevel opinions. However, in order to overcome the small n problem
for less populous states, they have aggregated a decade or more of
national surveys to construct their measures. For example, Erikson,
Wright and McIver (1993) pooled 122 national surveys conducted over 13
years to produce statelevel partisan and ideology estimates. Brace,
SimsButler, Arceneaux, and Johnson (2002) pooled 22 surveys over a
25year period to produce statelevel opinions on a number of specific
issues. We construct a hierarchical logistic regression model for the
mean of a binary response variable conditional on poststratification
cells. This approach combines the modeling approach often used in
smallarea estimation with the population information used in
poststratification (see Gelman and Little 1997). We produce statelevel
estimates pooling seven national surveys conducted over a nineday
period. We first apply the method to a set of U.S preelection polls,
poststratified by state, region, as well as the usual demographic
variables and evaluate the model by comparing it to statelevel election
outcomes. We then produce statelevel partisan and ideology estimates by
comparing it to Erikson, Wright and McIver's estimates. 

39 
Paper

A Bayesian Method for the Analysis of Dyadic Crisis Data
Smith, Alastair

Uploaded 
11041996

Keywords 
Bayesian model testing Censored data Crisis data Gibbs sampling Markov chain Monte Carlo Ordered discrete choice model Strategic choice

Abstract 
his paper examines the level of force that nations use during
disputes. Suppose that two nations, A and B, are involved in a
dispute. Each nation chooses the level of violence that it is prepared
to use in order to achieve its objectives. Since there are two
opponents making decisions, the outcome of the crisis is determined by
a bivariate rather than univariate process. I propose a bivariate
ordered discrete choice model to examine the relationship between
nation A's decision to use force, nation B's decision to use force,
and a series of explanatory variables. The model is estimated in the
Bayesian context using a Markov chain Monte Carlo simulation
technique. I analyze Bueno de Mesquita and Lalman's (1992) dyadically
coded version of the Militarized Interstate Dispute data (Gochman and
Moaz 1984). Various models are compared using Bayes Factors. The
results indicate that nation A's and nation B's decisions to use force
can not be regarded as independent. Bayesian model comparison show
that variables derived from Bueno de Mesquita's expected utility
theory (1982, 1985; Bueno de Mesquita and Lalman 1986, 1992) provide
the best explanatory variables for decision making in crises. 

40 
Paper

Bayesian and Likelihood Inference for 2 x 2 Ecological Tables: An Incomplete Data Approach
Imai, Kosuke
Lu, Ying
Strauss, Aaron

Uploaded 
12162006

Keywords 
Coarse data Contextual effects
Data augmentation EM algorithm Missing information principle
Nonparametric Bayesian Modeling.

Abstract 
Ecological inference is a statistical problem where aggregatelevel data are used to make inferences about individuallevel behavior. Recent years have witnessed resurgent interest in ecological inference among political methodologists and statisticians. In this paper, we conduct a theoretical and empirical study of Bayesian and likelihood inference for 2 x 2 ecological tables by applying the general statistical framework of incomplete data. We first show that the ecological inference problem can be decomposed into three factors: distributional effects which address the possible misspecification of parametric modeling assumptions about the unknown distribution of missing data, contextual effects which represent the possible correlation between missing data and observed variables, and aggregation effects which are directly related to the loss of information caused by data aggregation. We then examine how these three factors affect inference and offer new statistical methods to address each of them. To deal with distributional effects, we propose a nonparametric Bayesian model based on a Dirichlet process prior which relaxes common parametric assumptions. We also specify the statistical adjustments necessary to account for contextual effects. Finally, while little can be done to cope with aggregation effects, we offer a method to quantify the magnitude of such effects in order to formally assess its severity. We use simulated and real data sets to empirically investigate the consequences of these three factors and to evaluate the performance of our proposed methods. C code, along with an easytouse R interface, is publicly available for implementing our proposed methods. 

41 
Paper

Bayesian statistical decision theory and a critical test for substantive significance
Esarey, Justin

Uploaded 
09092009

Keywords 
inference ttest substantive significance Bayesian

Abstract 
I introduce a new critical test statistic, c*, that uses Bayesian statistical decision theory to help an analyst determine whether quantitative evidence supports the existence of a substantively meaningful relationship. Bayesian statistical decision theory takes a rational choice perspective toward evidence, allowing researchers to ask whether it makes sense to believe in the existence of a statistical relationship given how they value the consequences of correct and incorrect decisions. If a relationship of size c* is not important enough to influence future research and policy advice, then the evidence does not support the existence of a substantively significant effect. A replication of findings from the American Journal of Political Science and Journal of Politics illustrates that statistical significance at conventional levels is neither necessary nor sufficient to accept a hypothesis of substantive significance using c*. I also make software packages available for Stata and R that allow political scientists to easily use c* for inference in their own research. 

42 
Paper

Moving Mountains: Bayesian Forecasting As Policy Evaluation
Brandt, Patrick T.
Freeman, John R.

Uploaded 
04242002

Keywords 
Bayesian vector autoregression VAR policy evaluation conditional forecasting

Abstract 
Many policy analysts fail to appreciate the dynamic, complex causal
nature of political processes. We advocate a vector autoregression
(VAR) based approach to policy analysis that accounts for various
multivariate and dynamic elements in policy formulation and
for both dynamic and specification uncertainty of parameters. The
model we present is based on recent developments in Bayesian
VAR modeling and forecasting. We present an example based on work in
Goldstein et al. (2001) that illustrates how a full accounting of the
dynamics and uncertainty in multivariate data can lead to more
precise and instructive results about international mediation in
Middle Eastern conflict. 

43 
Paper

Not Asked and Not Answered: Multiple Imputation for Multiple Surveys
Gelman, Andrew
King, Gary
Liu, Chuanhai

Uploaded 
10271997

Keywords 
Bayesian inference cluster sampling diagnostics hierarchical models ignorable nonresponse missing data political science sample surveys stratified sampling multiple imputation

Abstract 
We present a method of analyzing a series of independent
crosssectional surveys in which some questions are not answered in
some surveys and some respondents do not answer some of the questions
posed. The method is also applicable to a single survey in which
different questions are asked, or different sampling methods used, in
different strata or clusters. Our method involves multiplyimputing
the missing items and questions by adding to existing methods of
imputation designed for single surveys a hierarchical regression model
that allows covariates at the individual and survey levels.
Information from survey weights is exploited by including in the
analysis the variables on which the weights were based, and then
reweighting individual responses (observed and imputed) to estimate
population quantities. We also develop diagnostics for checking the
fit of the imputation model based on comparing imputed to nonimputed
data. We illustrate with the example that motivated this project 
a study of preelection public opinion polls, in which not all the
questions of interest are asked in all the surveys, so that it is
infeasible to impute each survey separately. 

44 
Paper

Modeling Foreign Direct Investment as a Longitudinal Social Network
Jensen, Nathan
Martin, Andrew
Westveld, Anton

Uploaded 
07132007

Keywords 
foreign direct investment social network data longitudinal data hierarchical modeling mixture modeling Bayesian inference.

Abstract 
An extensive literature in international and comparative political economy has focused on the how the mobility of capital affects the ability of governments to tax and regulate firms. The conventional wisdom holds that governments are in competition with each other to attract foreign direct investment (FDI). Nationstates observe the fiscal and regulatory decisions of competitor governments, and are forced to either respond with policy changes or risk losing foreign direct investment, along with the politically salient jobs that come with these investments. The political economy of FDI suggests a network of investments with complicated dependencies.
We propose an empirical strategy for modeling investment patterns in 24 advanced industrialized countries from 19852000. Using bilateral FDI data we estimate how increases in flows of FDI affect the flows of FDI in other countries. Our statistical model is based on the methodology developed by Westveld & Hoff (2007). The model allows the temporal examination of each notion's activity level in investing, attractiveness to investors, and reciprocity between pairs of nations. We extend the model by treating the reported inflow and outflow data as independent replicates of the true value and allowing for a mixture model for the fixed effects portion of the network model. Using a fully Bayesian approach, we also impute missing data within the MCMC algorithm used to fit the model. 

46 
Paper

Did Illegally Counted Overseas Absentee Ballots Decide the 2000 U.S. Presidential Election?
Imai, Kosuke
King, Gary

Uploaded 
02132002

Keywords 
2000 U.S. Presidential Election Ecological Inference Bayesian Model Averaging

Abstract 
Although not widely known until much later, Al Gore received 202
more votes than George W. Bush on election day in Florida. George
W. Bush is president because he overcame his election day deficit
with overseas absentee ballots that arrived and were counted after
election day. In the final official tally, Bush received 537 more
votes than Gore. These numbers are taken from the official results
released by the Florida Secretary of State's office and so do not
reflect overvotes, undervotes, unsuccessful litigation, butterfly
ballot problems, recounts that might have been allowed but were not,
or any other hypothetical divergence between voter preferences and
counted votes. After the election, the New York Times conducted a
six month long investigation and found that 680 of the overseas
absentee ballots were illegally counted, and no partisan, pundit,
or academic has publicly disagreed with their assessment.
In this paper, we describe the statistical procedures we developed
and implemented for the Times to ascertain whether disqualifying
these 680 ballots would have changed the outcome of the election.
The methods involve adding formal Bayesian model averaging procedures
to King's (1997) ecological inference model. Formal Bayesian model
averaging has not been used in political science but is especially
useful when substantive conclusions depend heavily on apparently
minor but indefensible model choices, when model generalization is
not feasible, and when potential critics are more partisan than
academic. We show how we derived the results for the Times so that
other scholars can use these methods to make ecological inferences
for other purposes. We also present a variety of new empirical
results that delineate the precise conditions under which Al Gore
would have been elected president, and offer new evidence of the
striking effectiveness of the Republican effort to convince local
election officials to count invalid ballots in Bush counties and not
count them in Gore counties. 

47 
Paper

Testing Theories Involving Strategic Choice: The Example of Crisis Escalation
Smith, Alastair

Uploaded 
07231997

Keywords 
Strategic choice Bayesian model testing Markov chain Monte Carlo simulation multivariate probit crisis escalation war

Abstract 
If we believe that politics involves a significant
amount of strategic interaction then classical
statistical tests, such as Ordinary Least Squares,
Probit or Logit, cannot give us the right answers.
This is true for two reasons: The dependent variables
under observation are interdependent that is the
essence of game theoretic logic and the data is
censored  that is an inherent feature of off the
path expectations that leads to selection effects.
I explore the consequences of strategic decision making
on empirical estimation in the context of international
crisis escalation. I show how and why classical
estimation techniques fail in strategic settings.
I develop a simple strategic model of decision making
during crises. I ask what this explanation implies about
the distribution of the dependent variable: the level of
violence used by each nation. Counterfactuals play a key
role in this theoretical explanation. Yet, conventional
econometric techniques take no account of unrealized
opportunities. For example, suppose a weak nation (B) is
threatened by a powerful neighbor (A). If we believe that
power strongly influences the use of force then the weak
nation realizes that the aggressor's threats are probably
credible. Not wishing to fight a more powerful opponent,
nation B is likely to acquiesce to the aggressor's demands.
Empirically, we observe A threaten B. The actual level of
violence that A uses is low. However, the theoretical model
suggests that B acquiesced precisely because A would use force.
Although the theoretical model assumes a strong relationship
between strength and the use of force, traditional techniques
find a much weaker relationship. Our ability to observe whether
nation A is actually prepared to use force is censored when nation
B acquiesces. I develop a Strategically Censored Discrete Choice
(SCDC) model which accounts for the interdependent and censored
nature of strategic decision making. I use this model to test
existing theories of dispute escalation. Specifically, I analyze
Bueno de Mesquita and Lalman's (1992) dyadically coded version of
the Militarized Interstate Dispute data (Gochman and Moaz 1984).
I estimate this model using a Bayesian Markov chain Monte Carlo
simulation method. Using Bayesian model testing, I compare the
explanatory power of a variety of theories. I conclude that strategic
choice explanations of crisis escalation far outperform nonstrategic
ones. 

49 
Paper

Penalized Regression, Standard Errors, and Bayesian Lassos
Kyung, Minjung
Gill, Jeff
Ghosh, Malay
Casella, George

Uploaded 
02232010

Keywords 
model selection lassos Bayesian hierarchical models LARS algorithm EM/Gibbs sampler Geometric Ergodicity Gibbs Sampling

Abstract 
Penalized regression methods for simultaneous variable selection and coefficient estimation, especially those based on the lasso of Tibshirani (1996), have received a great deal of attention in recent years, mostly through frequentist models. Properties such as consistency have been studied, and are achieved by different lasso variations. Here we look at a fully Bayesian formulation of the problem, which is flexible enough to encompass most versions of the lasso that have been previously considered. The advantages of the hierarchical Bayesian formulations are many. In addition to the usual easeofinterpretation of hierarchical models, the Bayesian formulation produces valid standard errors (which can be problematic for the frequentist lasso), and is based on a geometrically ergodic Markov chain. We compare the performance of the Bayesian lassos to their frequentist counterparts using simulations and data sets that previous lasso papers have used, and see that in terms of prediction mean squared error, the Bayesian lasso performance is similar to and, in some cases, better than, the frequentist lasso. 

50 
Paper

Random Coefficient Models for TimeSeriesCrossSection Data: The 2001 Version
Beck, Nathaniel
Katz, Jonathan

Uploaded 
07172001

Keywords 
random coefficients generalized least squares empirical Bayesian Steinrule TCSC

Abstract 
This paper considers random coefficient models (RCMs) for
timeseriescrosssection data. These models allow for unit to unit
variation in the model parameters. After laying out the various
models, we assess several issues in specifying RCMs. We then consider
the finite sample properties of some standard RCM estimators, and show
that the most common one, associated with Hsaio, has very poor
properties. These analyses also show that a somewhat awkward
combination of estimators based on Swamy's work performs reasonably
well; this awkward estimator and a Bayes estimator with an
uninformative prior (due to Smith) seem to perform best. But we also
see that estimators which assume full pooling perform well unless
there is a large degree of unit to unit parameter heterogeneity. We
also argue that the various data driven methods (whether classical or
empirical Bayes or Bayes with gentle priors) tends to lead to much
more heterogeneity than most political scientists would like. We
speculate that fully Bayesian models, with a variety of informative
priors, may be the best way to approach RCMs. 

