A widespread tool in the context of a point null hypothesis significance testing framework is the computation of statistical power, especially in the planning stage of quantitative studies. However, asymptotic power formulas are often not readily available for certain tests, or are too...

Teaching and learning statistics and econometrics requires assessment through a problem set (PS). Often the PS requires some statistical analysis of a single database; therefore there is a unique answer. Although a unique answer guarantees the exercise was done correctly, it also facilitates...

Stata 13's new power command performs power and sample-size analysis. The power command expands the statistical methods that were previously available in Stata's sampsi command. I will demonstrate the power command and its additional features, including the support of multiple study scenarios...

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...

Measurement invariance is a very important requisite in multiple group structural equation modeling. It attempts to verify that the factors are measuring the same underlying latent constructs within each group. The presentation will show the use of the sem command in assessing six types of...

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...