How much money do people spend on graduation gifts? In 2007, a federation survey

Question

How much money do people spend on graduation gifts? In 2007, a federation surveyed 2415 consumers who reported that they bought one or more graduation gifts that year. The sample was selected in a way designed to produce a sample representative of adult Americans who purchased graduation gifts in 2007. For this sample, the mean amount spent per gift was $51.05. Suppose that the sample standard deviation was $20. Construct a 98% confidence interval for the mean amount of money spent per graduation gift in 2007. (Round your answers to three decimal places.) Interpret the interval. We are 98% confident that the mean amount of graduation money spent was within this interval. We are confident that the mean amount of money spent per graduation gift in 2007 was within this interval 98% of the time. We are confident that 98% of the amount of money spent per graduation gift in 2007 was within this interval. We are 98% confident that the mean amount of money spent per graduation gift in 2007 was within this interval.

Explanation / Answer

mean = 51.05 , s =20 , n =2415

z value at 98% CI = 2.33

CI = mean + / - z * (s /sqrt(n))

= 51.05 +/- 2.33 * ( 20 / sqrt(2415))

= (50.101, 51.998)

Answer is option D)

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