The mean life of a sample of 64 bulbs produced by a company is 1375 hours with standard deviation of

The mean life of a sample of 64 bulbs produced by a company is 1375 hours with standard deviation of 80 hours. If u is the mean life of all bulbs produced by the company, test the hypothesis 1400 against the alternative hypothesis uz 1400 hours at 5% level of significance​

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