Sometimes we have multiple measures of the same concept. Combining the information of these multiple measures would allow us to improve the measurement. When combining the information from different indicators one needs to distinguish between two types of relationships between the observed...

Sometimes one wants to model the effect of a variable as a nonlinear smooth curve. A convenient choice for such a curve is a restricted cubic spline. This option has existed in Stata for a while through user-written programs, but as of Stata 10, the mkspline command in combination with the cubic...

Stata has for a long time the capability of imposing the constraint that parameters are a linear function of one another. It does not have the capability to impose the constraint that if a set of parameters change (due to interaction terms) they will maintain the relative differences among them....

In this presentation, I discuss a method by Erikson et al. (2005) for decomposing a total effect in a logit model into direct and indirect effects, and I propose a generalization of this method. Consider an example where social class has an indirect effect on attending college through academic...

When dealing with response variables that are proportions, people often use regress. This approach can be problematic since the model can lead to predicted proportions less than zero or more than one and errors that are likely to be heteroskedastic and nonnormally distributed. This talk will...

In this talk, I will discuss some techniques available in Stata for analyzing dependent variables that are proportions. I will discuss four programs: betafit, glm, dirifit, and fmlogit. The first two deal with situations where we want to explain only one proportion, while the latter two deal...

The creation and testing of interaction terms in regression models can be very cumbersome, even in Stata 8. We propose a simple wrapping command, -fitint-, that fits any generalised linear model and tests any twoway interactions, as well as all main effects. There is no need to use -xi- because...

Among various structures in Stata for cycling through lists (whether lists of variable names, numbers, or arbitrary strings) are foreach and forvalues, introduced in Stata 7 in 2001, and for, introduced in Stata 3.1 in 1992, and revised in 5.0 (1997) and 6.0 (1999). Typically, each member of the...

Stata's matrix language, Mata, highlighted in Bill Gould's Mata Matters columns in the Stata Journal, is very useful and powerful in its interactive mode. Stata users who write do-files or ado-files should gain an understanding of the Stata-Mata interface: how Mata may be called upon to do one...