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1E: Degrees of freedom: WTF?!


With Jeff Witmer (Oberlin College)


Abstract

Degrees of Freedom are the Wrong Topic of Focus Getting the degrees of freedom right means getting the right p-value; but if you use the wrong df the p-value barely changes -- and you didn't need an exact p-value anyway. Other things are more important, so just use +/- 2 and don't worry about being more precise. Don't let mathematical pseudo-precision supplant statistical thinking. Rather than teach degrees of freedom and the like, what should we be teaching? Here is a starter list: Effect size The regression effect The sign test McNemar’s test (easier to understand than a paired t-test, and easier to do) Simpson's Paradox -- and controlling for confounders Bayesian inference -- at least an introduction There are many other things that could be listed here. We'll brainstorm, compare experiences, and maybe reach some level of agreement (or not).


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