1. A purchaser of electronic components wants to test the hypothesis that they last less than 100 h. To do this she takes a random sample of 16 such components and ?nds that, on average, they last 96 h, with a standard deviation of 8 h. If the purchaser knows that the lifetime of the components is normally distributed, should she accept the hypothesis that they last less than 100 h at
(a) A 95% level of con?dence?
(b) A 99% level of con?dence?
2. In the past, 20% of applicants for admission into a master's program had GRE scores above 650. Of the 88 students applying to be admitted into the program in 1981, 22 had GRE scores above 650. Do the 1981 applicants have greater GRE scores than previous applicants at the 5% level of signi?cance?