The number of books borrowed from a library each week follows a normal distribution. When a sample is taken for several weeks, t
he mean is found to be 190 and the standard deviation is 30. What is the percentage of the chance that more than 250 books were borrowed in a week? a. 99.7
b. 95
c. 13.5
d. 2.5
1 SD away from mean is 68% of data. 2 SD away from mean is 95% of data. 3 SD away from mean is 99.7% of data.
1 SD away: 190+30=220
2 SD away: 220+30=250
This shows we are on the outer 5 percent of the normal distribution. Since you said "more", that means we only look at the right side of your 5%, which is only 2.5%
