Biographical data gathered in surveys is often stored in spell format, allowing for overlaps between spell states. This gives useful information to researchers but leaves them with a very complex data structure, which is not easy to handle. I present my work on the ado-package newspell. It...

When one estimates discrete choice models, the mixed logit approach is commonly superior to simple conditional logit setups. Mixed logit models not only allow the researcher to implement difficult random components but also overcome the restrictive IIA assumption. Despite these theoretical...

We propose an estimator for models in which an endogenous dichotomous treatment affects a count outcome in the presence of either sample selection or endogenous participation using maximum simulated likelihood. We allow for the treatment to have an effect on both the participation or the sample...

When I first met Stata in October 2000, my golf handicap was 27 and my game was going nowhere slowly. Ten years of intensive Stata therapy later, my handicap is 17.3 and falling. It would, of course, be nonsense to infer from this data that lowering your handicap increases Stata use, but could...

I present the new Stata 12 command, mi impute chained, to perform multivariate imputation using chained equations (ICE), also known as sequential regression imputation. ICE is a flexible imputation technique for imputing various types of data. The variable-by-variable specification of ICE allows...

Functions in Stata range between those you know you want and those you don't know you need. The word "functions" is heavily overloaded in Stata; here the focus is on functions' strict sense, _variables, extended macro functions, and egen functions. Often Stata users in difficulty are seeking...

Background: Random effects are commonly modeled in multilevel, longitudinal, and latent-variable settings. Rather than estimating fixed effects for specific clusters of data, "predictions" can be made as the mode or mean of posterior distributions that arise as the product of the random effect...

Modern genetic genome-wide association studies typically rely on single nucleotide polymorphism (SNP) chip technology to determine hundreds of thousands of genotypes for an individual sample. Once these genotypes are ascertained, each SNP alone or in combination is tested for association...

Splines, including polynomials, are traditionally used to model nonlinear relationships involving continuous predictors. However, when they are included in linear models (or generalized linear models), the estimated parameters for polynomials are not easy for nonmathematicians to understand, and...

Multiple imputation is increasingly regarded as the standard method to account for partially observed data, but most methods have been based on cross-sectional imputation algorithms. Recently, a new multiple-imputation method, the two fold fully conditional specification (FCS) method, was...