The mean of a normal probability distribution is 500 and the standard deviation is 10. About 95% 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

The 95% confidence interval for a normal distribution is found by taking the mean +/- 1.96 times the standard deviation.

In this case, the mean is 500 and the standard deviation is 10.

So, the interval would be:

500 +/- 1.96(10) = 480 to 520

Therefore, the correct answer is B).

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