A researcher records the following time spent sleeping per night (in hours)in a group of participants: 5.8 ± 1.8 (M ± SD).The researcher decides to categorize participants who sleep between 6 and 8 hr as moderate sleepers.What percentage of participants fell in this category?
A) about 39%
B) about 11%
C) about 35%
D) about 7%

Question

Quizplus · Accepted Answer

To determine what percentage of participants are moderate sleepers (sleep between 6 and 8 hours), we need to calculate the number of participants falling within this range. 
6 hours (lower limit) minus the mean of 5.8 hours = 0.2/1.8 = 0.11 standard deviations above the mean. 
8 hours (upper limit) minus the mean of 5.8 hours = 2.2/1.8 = 1.22 standard deviations above the mean. 
Using a standard normal table, we can see that the percentage of participants falling within this range is approximately 34.13%. Therefore, the best choice is C, about 35%.

A Researcher Records the Following Time Spent Sleeping Per Night