Here’s a reveal – but please keep it secret. This is very important – if everyone knew what I am about to say, statistics wouldn’t be hard enough.
There are only two statistical tests in Psychology. Everything else is just for pretend. Here’s the real list:
- F test: if the DV is an Interval variable.
- chi-sqr test: if the DV is a Categorical variable or if either of the variables (IV or DV) is Ordinal.
So what about all the others? Well, in BrawStats (and I suspect SPSS, Jamovi, etc etc) the software does just those two tests, but then reports the results as if it had done the “official” test. It hasn’t; it is just pretending.
A bit of an explanation: Psychology has issues. It collects statistical tests, but can’t bring itself to declutter. It’s exactly like internet shopping: it sees a new test and buys it, without asking (i) whether it needs it and (ii) whether it can get rid of older stuff.
The two tests? Think of tests as being about seeing how much of what is going on in the DV can be epxlained by the IV.
- F test: how much
If the DV is Interval, we are looking at how much participants scored. F compares what scores we got compared with what scores we expected. - Chisqr test: how many
If the DV is Categorical, we are looking at how many participants were what. Chisqr compares how many we got with how many we expected to get.
That’s it.