SOLUTION: Question : The mean life time of a sample of 90 light bulbs produced by a company is computed to be 1570 hours with a standard deviation of 120 hours. If µ is the mean of all bul

Question 1173382: Question :
The mean life time of a sample of 90 light bulbs produced by a company is computed to be 1570 hours with a standard deviation of 120 hours. If µ is the mean of all bulbs produced by the company, test the hypothesis that µ is equal to 1600 hours against the alternative µ˂ 1600 hours.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
This would be 1 way with a z-statistic which at the 0.05 level would have a critical value z < -1.645
z=(x bar-mean)/sigma/sqrt(90)
=-30*sqrt(90)/120
=-2.37
reject Ho; there is evidence that the true mean is < 1600 hrs. p-value=0.009.
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