statistics
posted by Patrick .
The mean lifetime of a sample of 100 light tubes is 1570 hours with a standard deviation of 80 hours test the hypothesis that the mean lifetime of the tubes is 1600 hours

Z = (scoremean)/SEm
SEm = SD/√n
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability of the Z score.
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