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?

statistics 
PsyDAG,
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.