statistics
posted by Emily on .
Suppose the amount of time it takes for statistics students to complete their midterm is normally distributed with a mean of 85.70 minutes and a standard deviation of 22.55 minutes. If 10 students are randomly selected, what is the probability that they would average less than one and threequarter hours to take their midterm?

Z = (scoremean)/SEm
SEm = SD/√(n1)
Change all into minutes and calculate Z.
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score.