A. A manufacturer wants to increase the shelf life of a line of cake mixes. Past records indicate that the average shelf life of the mix is 223 days. After a revised mix has been developed, a sample of nine boxes of cake mix gave these shelf lives (in days): 222,225, 226, 227, 224, 229, 230, 230, and 227. Using = 0.025, has the shelf life of the cake mix increased? Why?

B. The average cost of tuition plus room and board for a small private liberal arts college is reported to be $8,600 per term, but a financial administrator believes that the average cost is higher. A study conducted using 350 small liberal arts colleges showed that the average cost per term is $8,855. The population standard deviation is $1,200. Let = 0.05. Based on the computed test statistic or p-value, what is our decision about the average cost?