logoPicV1 logoTextV1

Search Results

Below results based on the criteria 'extrapolation'
Total number of records returned: 3

Death by Survey: Estimating Adult Mortality without Selection Bias
King, Gary
Gakidou, Emmanuela

Uploaded 07-14-2005
Keywords surveys
selection bias
mortality data
international relations
Abstract The widely used methods for estimating adult mortality rates from sample survey responses about the survival of siblings, parents, spouses, and others depend crucially on an assumption that we demonstrate does not hold in real data. We show that when this assumption is violated -- so that the mortality rate varies with sibship size -- mortality estimates can be massively biased. By using insights from work on the statistical analysis of selection bias, survey weighting, and extrapolation problems, we propose a new and relatively simple method of recovering the mortality rate with both greatly reduced potential for bias and increased clarity about the source of necessary assumptions.

The Dangers of Extreme Counterfactuals
King, Gary
Zeng, Langche

Uploaded 07-18-2005
Keywords propensity score
convex hull
model dependence
Abstract We address the problem that occurs when inferences about counterfactuals -- predictions, ``what if'' questions, and causal effects -- are attempted far from the available data. The danger of these extreme counterfactuals is that substantive conclusions drawn from statistical models that fit the data well turn out to be based largely on speculation hidden in convenient modeling assumptions that few would be willing to defend. Yet existing statistical strategies provide few reliable means of identifying extreme counterfactuals. We offer a proof that inferences farther from the data are more model-dependent, and then develop easy-to-apply methods to evaluate how model-dependent our answers would be to specified counterfactuals. These methods require neither sensitivity testing over specified classes of models nor evaluating any specific modeling assumptions. If an analysis fails the simple tests we offer, then we know that substantive results are sensitive to at least some modeling choices that are not based on empirical evidence. The most recent version of this paper and software that implements the methods described is available at http://gking.harvard.edu.

Extracting Systematic Social Science Meaning from Text
Hopkins, Daniel
King, Gary

Uploaded 07-12-2007
Keywords automated content analysis
machine learning
simulated extrapolation
non-parametric estimation
2008 U.S. Presidential election
Abstract We develop two methods of automated content analysis that give approximately unbiased estimates of quantities of theoretical interest to social scientists. With a small sample of documents hand coded into investigator-chosen categories, our methods can give accurate estimates of the proportion of text documents in each category in a larger population. Existing methods successful at maximizing the percent of documents correctly classified allow for the possibility of substantial estimation bias in the category proportions of interest. Our first approach corrects this bias for any existing classifier, with no additional assumptions. Our second method estimates the proportions without the intermediate step of individual document classification, and thereby greatly reduces the required assumptions. For both methods, we also correct statistically, apparently for the first time, for the far less-than-perfect levels of inter-coder reliability that typically characterize human attempts to classify documents, an approach that will normally outperform even population hand coding when that is feasible. We illustrate these methods by tracking the daily opinions of millions of people about candidates for the 2008 presidential nominations in online blogs, data we introduce and make available with this article, and through evaluations in available corpora from other areas, including movie reviews, university web sites, and Enron emails. We also offer easy-to-use software that implements all methods described.

< prev 1 next>