statistics
posted by Hannah on .
The average score on a science test was 72 with a standard deviation of 6. The average score on a history test was 89 with a standard deviation of 7. Compare the variability of the two classes.

7. The average length of time per week that students at this university spend on homework is normally distributed with a mean of 18 hours and a standard deviation of 3 hours. If Diane spends more time on homework each week than 75% of students, what is the minimum time she must spend?