The mean of a normal probability distribution is 500 and the standard deviation is 10. About 95 percent of the observations lie between what two values?
A) 475 and 525
B) 480 and 520
C) 400 and 600
D) 350 and 650

Question

Quizplus · Accepted Answer

In a normal distribution, 95% of the observations fall within 1.96 standard deviations of the mean. Therefore, the range of values between which 95% of the data lies is:
500 - (1.96 x 10) and 500 + (1.96 x 10)
= 480 and 520
Hence, the best choice is B which includes the range 480 and 520.

The Mean of a Normal Probability Distribution Is 500 and the Standard