Reconsider the previous exercise about the potential confounding variable that provides an alternative explanation for why the all-nighter group would have a significantly lower average GPA. Sketch a well-labeled diagram showing how this explanation works.

Data from previous exercise

Suppose that the difference between these two averages (3.1 vs. 2.9) is shown to be statistically significant. Which of the following is a potential confounding variable and provides an alternative explanation for why the all-nighter group would have a significantly lower average GPA?

Refer to a study published in the January 2008 issue of Behavioral Sleep Medicine that involved a survey of 120 students at St. Lawrence University, a small liberal arts college in upstate New York.