Question 360219
A product has a mean life of 660 hours, and a standard deviation of 45 hours. A business buys 100 such products at random. What is the probability that the mean life of those 100 products would be greater than 650 hours? 
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t(650) = (650-660)/[45/sqrt(100)] = -2.2222
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P(x-bar > 650) = P(t > -2.2222 when df = 99) = 0.9857
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Cheers,
Stan H.