Selecting the right test

At this moment you should be able to identify cases involving comparisons between one, two or more samples.

When you are interested for testing for significant differences in the cases above you have have to select among tests called Z-test, T-test or the ANOVA (also so-called analysis if variances).

Which test you should use is based primarily on the number of samples you have, whether you know the variance of your population and whether the sample size is larger than 30 individuals or not.

You need to use the following chart to select the proper test. Please remember that these are parametric tests, meaning they are only useful for cases in which data are normally distributed.

Figure 9.2: Selecting statistical test

Also take a moment to review how hypotheses are stated, as that will be important in a moment to select the right type of test.