A sociologist studying freshmen carried out a survey, asking, among other questions, how often students went out per week, how many hours they studied per day, and how many hours they slept at night.

The tables provide the answers on the time slept and the time spent studying by whether or not students went out.

Go out Hours/day studied Hours slept less than 6 Hours slept 6 or more Total Stay in dorm Hours/day studied Hours slept less than 6 Hours slept 6 or more Total Less than 2 3 9 12 Less than 2 40 120 160 2 or more 14 14 28 2 or more 20 20 40 Total 17 23 40 Total 60 140 200

When we examine the data, we find that students who studied more slept less, both among those who go out and among those who stay in the dorm.

When we combine both groups of students, we find that those who studied more also slept more.

This is an example of:

a. Simpson's Paradox.

b. Andersen's Paradox.

c. the Probability Paradox.

d. the Gaussian Paradox.