Dullco Manufacturing Claims That Its Alkaline Batteries Last at Least

Multiple Choice

Dullco Manufacturing claims that its alkaline batteries last at least 40 hours on average in a certain type of portable CD player. But tests on a random sample of 18 batteries from a day's large production run showed a mean battery life of 37.8 hours with a standard deviation of 5.4 hours. To test DullCo's hypothesis, the test statistic is:

A) -1.980
B) -1.728
C) -2.101
D) -1.960