We all know that studying helps you do better on exams, but is that effect moderated by how much sleep you get the night before the exam takes place?

To answer this, researchers conducted an experiment on students in aBiostatistics class. The night before taking an exam, 60 students were randomly divided into 2 groups: a "no sleep" group was kept up all night, and a "high sleep" group was allowed to sleep 8 hours.

In addition to their exam grades (ranging from 0-100), the researchers also measured how many hours each student studied for the exam. They confirmed all relevant assumptions and ran a multiple linear regression, including interaction, with the following results: