The mean length of time, per week, that students at a certain school spend on their homework is 24.3 hours, with a standard deviation of 1.4 hours. Assuming the distribution of study times is normal, what percent of students study between 22.9 and 25.7 hours?
A) 99.7%
B) 95%
C) 68%
D) 50%

Question

Quizplus · Accepted Answer

This question involves the empirical rule (68-95-99.7 rule) for normal distributions, which states that approximately 68% of the data falls within one standard deviation of the mean. Here, 22.9 hours and 25.7 hours are one standard deviation away from the mean (24.3 hours ± 1.4 hours), so approximately 68% of students study between these times.

The Mean Length of Time, Per Week, That Students at a Certain