Stage 2 · Lesson 7 of 8
Choosing the right test
The test follows from the question and the data type. Comparing two group means: a Welch , which does not assume equal . The same people measured twice: a paired t-test.
Two proportions, such as : a z-test or chi-square test. Skewed or ranked data: the Mann-Whitney U test. Three or more group means: .
Two numeric variables moving together: correlation. Keep a small table of these and practise picking from a description before you touch code. In Python they live in SciPy and ; in R most are built in.
Common traprunning an independent t-test on paired data, before and after for the same people, which throws away the pairing and most of your power to see a real change.
A question to check yourself, an AI practice session and 1 cheat sheet entry come with the full roadmap. Unlock
Resources for this stage
Start with· follow one of these
- VideoFreeStatQuest with Josh Starmer
StatQuest · Beginner
Free: short, clear videos on each concept, from the normal distribution to p-values and power
- CourseFreeKhan Academy Statistics and Probability
Khan Academy · Beginner
Free: the probability, sampling distributions, confidence intervals and significance tests units, with practice
Practise
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Interactive visuals for probability, distributions, inference and regression: play with each one