A typical statistics section

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Many methods sections include the sentence “Normally distributed variables were compared with the independent groups t-test”. The sentence is problematic for a number of reasons. First, statistical tests are not performed in order to compare observed variables. They are performed in order to test hypotheses about the population represented by the studied sample. Second, how can the author know whether or not a variable is normally distributed in the population represented by the studied sample? The author can only assume that the distribution is normal. The assumption can perhaps be supported by the outcome of a statistical test, but the result will nevertheless be uncertain. Third, the independent groups t-test is a description in SPSS and perhaps also in some other software packages, but the description is vague because several t-test for independent groups have been developed, e.g. Student’s, Satterthwaite’s, Welch’s, Prien’s, etc.