Psychology is weird. Some of the most important and useful insights involve things that nobody can observe — things that go on in your head — events that only you witness. And yet our most developed theories were developed to predict observable behaviour, not hidden thoughts and feelings.

I live this conundrum on a daily basis.

As a coaching psychologist (and as a human being) my main psychological interest is in self-development through regulating our own thoughts and behaviours. Learning to meditate changed my life. Of course, what it mostly changed was how I deal with my own thoughts and bodily sensations. As an Associate Professor of Psychological Measurement and Statistics, I spend large parts of my life trying to figure out how we can accurately measure, understand, and teach such self-development processes.

Until we have the sort of brain scanners only found in sci-fi, our best bet is psychometric measurement.

Choosing a statistical test: A cheat sheet

Students who are new to statistics tend to find it tricky to remember which test to use under which circumstances. The following diagram is intended as a decision aid only. There are many many more statistical tests that are not shown here, but these are the basic ones most commonly taught on psychology courses.

Even if you end up finding out that you need a more complex or niche statistical test, an aide memoire like this can still be useful if it reminds of the relevant keywords to search.

Remember, always check the assumptions of the test you choose.