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 17 stores this year shows mean sales of 57 units of a small appliance, with a standard deviation of 11 units. During the same point in time last year, an SRS of 10 stores had mean sales of 68.99 units, with standard deviation 10 units. A decrease from 68.99 to 57 is a drop of about 21%. 1. Construct a 99% confidence interval estimate of the difference u - H2, Wwhere u is the mean of this year's sales and u is the mean of last year's sales. (a) < (41 - 42) < (b) The margin of error is 2. At a 0.01 significance level, is there sufficient evidence to show that sales this year are different from last year? O A. Yes OB. No

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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 17 stores this year shows mean sales of 57
units of a small appliance, with a standard deviation of 11 units. During the same point in time last year, an SRS of 10 stores had mean
sales of 68.99 units, with standard deviation 10 units. A decrease from 68.99 to 57 is a drop of about 21%.
1. Construct a 99% confidence interval estimate
the difference u - 42, where uj is the mean of this year's sales and uz is the mean of
last year's sales.
(a)
E < (41 – 42) <
(b) The margin of error is
2. At a 0.01 significance level, is there sufficient evidence to show that sales this year are different from last year?
OA. Yes
B. No
Transcribed Image Text: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 17 stores this year shows mean sales of 57 units of a small appliance, with a standard deviation of 11 units. During the same point in time last year, an SRS of 10 stores had mean sales of 68.99 units, with standard deviation 10 units. A decrease from 68.99 to 57 is a drop of about 21%. 1. Construct a 99% confidence interval estimate the difference u - 42, where uj is the mean of this year's sales and uz is the mean of last year's sales. (a) E < (41 – 42) < (b) The margin of error is 2. At a 0.01 significance level, is there sufficient evidence to show that sales this year are different from last year? OA. Yes B. No
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