Degrees of freedom (df)

Degrees of freedom depend mostly on the number of people. They determine which reference distribution is used. In the APA line they appear in parentheses.

Example: t(118): 120 people minus 2 groups. For Welch's test they are often a decimal number, here t(77.46).

Caution: That is usually all you need to know about degrees of freedom. They belong in every report, though, so others can check the result.