Suppose that the quality control engineer in question 35 does not know what the standard deviation is and that this time, he selects a random sample of only 25 light bulbs. Does your answer to question 35 change? Explain.

Question 35

A quality control engineer is interested in testing the mean life of a new brand of light bulbs. A sample of 100 light bulbs is taken, and the sample mean life of these light bulbs is found to be 1,075 h. Suppose the standard deviation is known and is 100 h. Use a .05 level of significance to test the hypothesis that the mean life of the new bulbs is greater than 1,000 h.