Previous trial has shown that starting ART therapy earlier (‘Early’) rather than waiting for onset of symptoms (‘Standard’) in HIV patients significantly decreases mortality. As a follow-up, researchers are interested in determining if ‘Early’ therapy significantly decreases time to...

Testing for the presence of autocorrelation in a time series is a common task for researchers working with time series data. The standard Q test statistic, introduced by Box and Pierce (1970) and refined by Ljung and Box (1978), is applicable to univariate time series and to testing for...

Inspired in the R library 'snow' and to be used in multicore CPUs, parallel implements parallel computing methods through an OS's shell scripting (using Stata in batch mode) to accelerate computations. By splitting the dataset into a determined number of clusters this module repeats a task...

Stata’s sem command includes the ability to estimate models with missing data using full information maximum likelihood estimation (FIML). One of the assumptions of FIML is that the data is at least missing at random (MAR), that is, conditional on other variables in the model, missingness is...

Fractals are some of the most beloved and recognizable mathematical objects studied. They have been traced as far back as Leibniz, but failed to receive rigorous examination until the mid-twentieth century with the many publications of Benoit Mandelbrot and the advent of the modern computer. The...

This presentation will describe a protocol we have developed for teaching students conducting empirical research to document their work in such a way that their results are completely reproducible and verifiable. The protocol is comprised primarily of creating and assembling a collection of...

GPS coordinates are collected by many organizations, however in order to derive any meaningful statistical analysis from these coordinates they need to be joined with geographical data. Previously users were required to export the GPS data out of Stata and into a GIS mapping program to map the...

When estimating 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...

At last year’s Stata Conference, I presented some ideas for combining Stata and Python within a single interface. Two methods were presented; in one, Python was used to automate Stata, and in the other, Python was used to send simulated keystrokes to the Stata GUI. The first method has the...

This presentation provides a Stata application for the estimation of Blundell, Banks and Lewbel’s (1997) demand system, dealing with the zero problem which is in the heart of many expenditure survey analysis. Starting from Poi’s (2008) routine, our main contribution is the multivariate...