A special industrial battery must have a life of at least 400 hours. A hypothesis test is to

be conducted with a 0.02 level of significance. If the batteries from a particular production

run have an actual mean use life of 385 hours, the production manager wants a sampling

procedure that only 10% of the time would show erroneously that the batch is acceptable.

What sample size is recommended for the hypothesis test? Use 30 hours as an estimate of

the population standard deviation.