posted by Colby on .
If you are told the mean grade in ECON 2023 is 80 with a standard deviation of 5, what is the probability that if you randomly selected 36 students you would find an average grade of 82 or more?
I found the Z-score: 82-80/5
Which gave me .6554 then 1-.6554=.3446
So 34% would make a 82 or more
You are looking for a distribution of means rather than raw scores.
Z = (score-mean)/SEm
SEm = SD/√n
Now go to your Z table.