Question: The Transit Authority of NYC uses tens of thousands of light bulbs every year. The brand that has been used up to now has a mean life of 1000 hours with a standard deviation of 90 hours. A new brand is offered to the Transit Authority at a price much lower than what it has been paying. The Authority decides that the new brand should be bought unless its mean life is less than 1000 hours at (alpha symbol) =0.05. Subsequently, 100 bulbs of the new brand are tested, yielding an average of 990 hours. Assuming that the standard deviation of the new brand is the same as that for the old, verify that the Authority will select the act of buying the new brand since z+11.