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. A random sample of 36 stores this year shows mean sales of 51 units of a small appliance with a standard deviation of 15 units. During the same point in time last year, a random sample of 49 stores had mean sales of 37 units with standard deviation 12 units. It is of interest to construct a 95 percent confidence interval for the difference in population means ?1−?2, where ?1 is the mean of this year's sales and ?2 is the mean of last year's sales. Enter values below rounded to three decimal places. (a) The estimate is: (b) The standard error is:
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. A random sample of 36 stores this year shows
It is of interest to construct a 95 percent confidence interval for the difference in population means ?1−?2, where ?1 is the mean of this year's sales and ?2 is the mean of last year's sales.
Enter values below rounded to three decimal places.
(a) The estimate is:
(b) The standard error is:
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