Jeff Witmer (Oberlin College)
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).