Let's say that the grades on this exam are normally distributed with a mean of 70 and a standard deviation of 10. Approximately what percentage of students will have a grade between 50 and 90 on this exam?
A)50 percent
B)95 percent
C)99 percent
D)80 percent
E)Can't tell from this information

Question

Quizplus · Accepted Answer

Using the 68-95-99.7 rule for normal distributions, approximately 95% of observations fall within two standard deviations of the mean. Since 50 and 90 are two standard deviations away from the mean (70 ± 2*10), about 95% of students' grades will fall in this range.

Let's Say That the Grades on This Exam Are Normally