Solve the problem (a) state the null and the alternative hypothesis, (b) determine the type of test, critical value and the rejection region, (c) compute the test value, (d) make a decision, and (e) draw a conclusion. Show the step by step procedure.

41 -50) A company which produces batteries claims that the life expectancy of their batteries is 90 hours. In order to test the claim, a consumer interest group tested a random sample of 4D batteries. The test resulted to a mean life expectancy of 87 hours. Using a 0.05 level of signicance. can it be concluded that the life expectancy of their batteries is less than 90 hours? Assume that the population standard deviation is known to be 10 hours