Posted by Jennifer on .
suppose that the times taken to complete an online test are normally distributed with a mean of 45 minutes and a standard deviation of 12 minutes. find the probability
a. that for a randomly selected test, the time taken was more than 1 hour.
b. that the mean number of minutes taken by a random sample of 24 tests is less than 50 minutes

probability 
PsyDAG,
a. Z = (scoremean)/SD
b. Z = (scoremean)/SEm
SEm = SD/√n
For each, find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score.