Question

(1 point) A market research firm supplies manufacturers with estimates of the retail sales of their products from samples of retail stores. Marketing managers are prone to look at the estimate and ignore sampling error. An SRS of 3131 stores this year shows mean sales of 5959 units of a small appliance, with a standard deviation of 55 units. During the same point in time last year, an SRS of 2929 stores had mean sales of64.4564.45 units, with standard deviation 6.16.1 units. A decrease from 64.4564.45 to 5959 is a drop of about 9%.

1. Construct a 99% confidence interval estimate of the differenceμ1−μ2μ1−μ2, where μ1μ1 is the mean of this year's sales and μ2μ2 is the mean of last year's sales.

(a)   <(μ1−μ2)<<(μ1−μ2)<

(b) The margin of error is  .

2. At a  0.010.01 significance level, is there sufficient evidence to show that sales this year are different from last year?

A. No
B. Yes

Answer 1