statistics
posted by Sunshine on .
Scores on a visual perception test are normally distributed with a mean of 2020 and a standard deviation of 250.
a)If one subject is randomly selected and tested, find the probability of a score greater than 1800
b)if 50 subjects are randomly selected and tested fid the probability that the sample mean is between 2000 and 2100

a) Z = (scoremean)/SD
b) Z = (scoremean)/SEm
SEm = SD/√n
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions/probabilities related to the Z scores.