8.2.10) The average selling price of a smartphone purchased by a random sample o

Question

8.2.10) The average selling price of a smartphone purchased by a random sample of 45 customers was $321. Assume the population standard deviation was $32.

a. Construct a 95% confidence interval to estimate the average selling price in the population with this sample. The 95% confidence interval has a lower limit of ___ and an upper limit of ___.

(Round to the nearest cent as needed.)

b. What is the margin of error for this interval?

8.2.8) Construct a 99% confidence interval to estimate the population mean using the following data. What assumptions need to be made to construct this interval?

x=84 , =19 , n=21

a) The 99%, when n=21 the population mean is between the lower limit of ___ and an upper limit of ___. (Round to the nearest cent as needed.)

8.2.13) Suppose a retailer claims that the average wait time for a customer on its support line is 173 seconds. A random sample of 43 customers had an average wait time of 164 seconds. Assume the population standard deviation for wait time is 47 seconds. Using a 95% confidence interval, does this sample support the retailer's claim?

Using a 95% confidence interval, does this sample support the retailer's claim? Select the correct choice below, and fill in the answer boxes to complete your choice.

(Round to two decimal places as needed.)

A. Yes, because the retailer's claim is between the lower limit of ____ seconds and the upper limit of ____ seconds for the mean wait time.

B. No, because the retailer's claim is not between the lower limit of ____ seconds and the upper limit of ____ seconds for the mean wait time.

Explanation / Answer

8.2.10) a)

95% Confident the population mean is within the range:
311.6504 < mean <330.3496

b)

Margin of error, E = 9.349565

8.2.8.)

a)

Margin of error, E = 10.67974

99% Confident the population mean is within the range:
73.32026 < mean <94.67974

8.2.13)

H0: the average wait time for a customer on its support line is 173

H1 : the average wait time for a customer on its support line is not 173

Margin of error, E = 14.0479

95% Confident the population mean is within the range:
149.9521 < mean <178.0479

The population Mean is 173 which is included in the 95% confidence interval.

So We accept H0

Thus, the population mean is 173

Correct Answer: Option A. Yes, because the retailer's claim is between the lower limit of 149.9521seconds and the upper limit of 178.0479seconds for the mean wait time.

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