Saud examined differences in reading ability between those who were exposed to parent read aloud and those who were exposed to sibling read aloud. To calculate histtest to compare groups, Saud needed to determine his degrees of freedom. To do so he will need to know not only that he has two groups but also he will need to know which of the following pieces of information?

The number of children in the study.

The number of parents in the study.

The mean group performance.

The mean number of treatment sessions.