Z = (score-mean)/SEm
SEm = SD/√(n-1)
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.
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 three-quarter hours to take their midterm?
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1 answer