You want to test whether your business costs are statistically different from last year. You sample100 products that you buy and take the differences in prices. The mean difference in price is $.45,and the standard deviation is $4.76. You interpret this standard deviation as the population standarddeviation.

(a) What is the hypothesis that you want to test?

(b) Calculate the test statistic.

(c) Test your hypothesis at the 95% level ( = .05). Verbally describe the result.

(d) Suppose, instead, that you believed your costs were higher. What is the new hypothesis? Test itat the 90% level ( = .1).