How can I remember when each statistical test should be used?

At A-Level there are eight different statistical tests that you need to be aware of.
Chi-square: Used for nominal data and independent groups, also used for nominal data and a correlation Sign Test: Nominal data with either matched pairs or repeated measures Mann-Whitney: Ordinal data and independent groupsWilcoxon: Ordinal data and matched pairs of repeated measures Spearsman's Rho: Ordinal data and a correlationUnrelated T-Test: Interval/Ratio data and independent groupsRelated T-Test: Interval/Ration data and matched pairs or repeated measuresPearson's R: Interval/ratio data and a correlation
You need to remember that the table displaying these statistical tests has a top row ordered: Independent groups, matched pairs/repeated measures and then correlation/relationship. The left hand side column has: nominal, ordinal and then interval/ratio. With this in mind, there is an easy saying to remember when each statistical test should be used: Carrots Should Come Mashed With Swede Under Roast Potatoes.
If you can't remember them all don't worry though as the points awarded for this section of the course won't be higher than four and you can still get marks from identifying the type of data, experimental design and if the researcher is looking for a difference or correlation.