This section covers some basic aspects of statistical analysis which are very often encountered in the course of any student’s normal progression. Most of the time, it is about comparing two or more groups to define whether there exists a difference or an association while considering a specific parameter or variable. But it isn’t only about that. It is important to understand a few concepts about the data to analyse. What is your dataset made of? What do you expect? What do you want to know? How much or what do you already know about the data?
The following screenshot was taken from the datasheet bound to the package TeachingDemos. It reduces the problem of choice between z-test and t-test to “in real life, no one use z-test !”. Just so that you know…