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 table below provides the answers on the time slept and the time spent studying. Among the students who studied 4 or more hours, what proportion slept less than 6 hours a night?
A)0.29
B)0.08
C)0.4
D)0.2

Question

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 table below provides the answers on the time slept and the time spent studying.  Among the students who studied 4 or more hours, what proportion slept less than 6 hours a night?
A)0.29 
B)0.08 
C)0.4 
D)0.2

Quizplus · Accepted Answer

Out of the students who studied 4 or more hours, there are a total of 18+11+3=32 students who slept less than 6 hours (adding up the values in the cells where studying is 4 or more hours and sleeping is less than 6 hours). Out of the students who studied 4 or more hours, there are a total of 18+11+3+15+3=50 students (adding up the values in the cells where studying is 4 or more hours). Therefore, the proportion of students who slept less than 6 hours given that they studied 4 or more hours is 32/50 which simplifies to 0.4 or 40%. Hence, the answer is C.

A Sociologist Studying Freshmen Carried Out a Survey, Asking (Among