# probability

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

1. a. Z = (score-mean)/SD

b. Z = (score-mean)/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.

posted by PsyDAG

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