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Statistical Software

(To download either of these software packages, use the save link as... or save target as... option on your browser.)

CLARIFY: Software for Interpreting and Presenting Statistical Results (version 2.1, January 5, 2003)

by Michael Tomz, Jason Wittenberg, and Gary King. Clarify uses Monte Carlo simulation to convert the raw output of statistical procedures into results that are of direct interest to researchers. The program, designed for use with the Stata statistics package, offers an easy way to implement the techniques described in Gary King, Michael Tomz, and Jason Wittenberg, "Making the Most of Statistical Analyses: Improving Interpretation and Presentation" American Journal of Political Science 44, no. 2 (April 2000): 347-61. Clarify was published in the Journal of Statistical Software 8, no. 1 (2003).

The current version of Clarify simulates quantities of interest for the most commonly used statistical models, including linear regression, binary logit, binary probit, ordered logit, ordered probit, multinomial logit, Poisson regression, negative binomial regression, the weibull duration model, and systems of seemingly unrelated regression equations. It also allows analysis of compositional data, including multiparty elections, as described in Michael Tomz, Joshua Tucker, and Jason Wittenberg, "An Easy and Accurate Regression Model for Multiparty Electoral Data" Political Analysis 10, no. 1 (Winter 2002): 66-83. Subsequent versions of Clarify will compute quantities of interest for other statistical models.

To install Clarify, remove previous versions from your computer and then type "net from" at the Stata command line. You will then be prompted to type "net install clarify", which will download all necessary files and install them in the proper location on your hard drive. We also provide a zip archive for users who want to install Clarify on a computer that is not connected to the internet.

Full documentation is available here. You may also be interested in slides from a half-day course on "Interpreting and Presenting Statistical Results."

Clarify won the 1999 APSA Award for the Best Research Software in Political Science.


ReLogit: Rare Events Logistic Regression (version 2.0, January 25, 2003)

by Michael Tomz, Gary King, and Langche Zeng. ReLogit is a suite of programs for estimating and interpreting logit results when the sample is unbalanced (one outcome is rarer than the other) or has been selected by a rule correlated with the dependent variable. The program, designed for use with the Stata statistics package, offers a convenient way to implement the procedures suggested in Gary King and Langche Zeng, "Logistic Regression in Rare Events Data." Relogit was published in the Journal of Statistical Software 8, no. 2 (2003).