One of those “rules” about statistics you often hear is that you can’t interpret a main effect in the presence of an interaction.

Stats professors seem particularly good at drilling this into students’ brains.

Unfortunately, it’s not true. 

At least not always. [click to continue…]

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The Difference Between a Chi-Square Test and a McNemar Test

You may have heard of McNemar tests as a repeated measures version of a chi-square test of independence. This is basically true, and I wanted to show you how these two tests differ and what exactly, each one is testing.

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A Primer in Matrix Algebra for Data Analysts Webinar

At the center of multivariate statistical methods is the simultaneous consideration of multiple variables and the inherent complexity it introduces. Matrix/Linear algebra is a mathematical method particularly well-suited to dealing with multiple variables…

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Argggh! How Do I Output Tables and Graphs From Stata?

On my first assignment using Stata, I think I spent four or five hours trying to present my output in a “professional” form. The most creative method I heard about in class the next day was to copy the contents into Excel, create page breaks and then copy into Word.

SPSS makes it so easy to copy tables and graphs into another document. Why can’t Stata be easy?

Anyone who has used Stata has gone through this and many of you still are. No worries, help is on the way!..

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Loops in Stata: Making coding easy

We’ve already discussed using macros in Stata to simplify and shorten code.

Another great tool in your coding tool belt is loops. Loops allow you to run the same command for several variables at one time without having to write separate code for each variable.

This discussion could go on for pages and pages because there is much you can do with a loop…

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Macros in Stata, Why and How to Use Them

We finished the last blog with the confusing coding of:

local continuous educatexper wage age
foreachvar in `continuous'{
graph box `var’, saving(`var’,replace)

I admit it looks like a foreign language. Let me explain how simple it is to understand..

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Using Stata Efficiently to Understand Your Data

Most statistical software packages use a spreadsheet format for viewing the data. This helps you get a feeling for what you will be working with, especially if the data set is small. But what if your data set contains numerous variables and hundreds or thousands of observations? There is no way you can get warm and fuzzy by browsing through a large data set.

To help you get a good feel for your data you will need toutilize your software’s command or syntax editor to write a series of code for reviewing your data. Sounds complicated…

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How to Get SPSS GENLINMIXED Output Without the Model Viewer

So I was glad that SPSS became an option for generalized linear mixed models.

But that Model Viewer had led me to nearly give up that option. It’s that annoying. (Google it if you’re curious about the hate for the Model Viewer).

Anyway, there is now a way to get rid of it.

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Model Building Strategies: Step Up and Top Down

How should I build my model?

I get this question a lot, and it’s difficult to answer at first glance–it depends too much on your particular situation. There are really three parts to the approach to building a model: the strategy, the technique to implement that strategy, and the decision criteria used within the technique.

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Why Use Stata?

Like many people with graduate degrees, I have used a number of statistical software packages over the years. Through work and school I have used Eviews, SAS, SPSS, R and Stata. Some were more difficult to use than others but if you used them often enough you would become proficient to take on the task at hand (though some packages required greater usage of George Carlin’s 7 dirty words). There was always one caveat which determined which package I used…

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