Question

Assume the weights of men are normally distributed having a mean of 185 lbs and a standard deviation of 17 pounds.
A. Calculate the probability a randomly selected man weights less than 225 lbs
B. Approximately 72% of men’s weights exceed how many pounds.
C. In a random example of 50 men, calculate the probability their mean weights is no more than 180 pounds.
D. In a random example of 50 men, approximately 8% of all possible men’s weights will exceed how many pounds.

Answer 1

A, B. Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability (B use.72) related to the Z score.

Last two problems relate to distribution of means rather than a distribution of raw scores.

C, D. Z = (score-mean)/SEm

SEm = SD/√n

Use same table.