23.27 Holiday spending. An October 2015 Gallup Poll asked a random sample of 1015 American adults “Roughly how much money do you think you personally will spend on Christmas gifts this year?” The mean holiday spending estimate in the sample was $\bar{x} = 812$

(a) Give a 95% confidence interval for the mean holiday spending estimate based on these data.
(b) The mean holiday spending estimate of $\bar{x} = 812$

23.27 (a) $802.77 to $821.23. (b) Because all respondents who answered No opinion were recorded as $0, and this group is likely to include people who will spend money on Christmas gifts but are unsure about the amount, the sample mean of $812 is likely to be too low. Thus, we should be skeptical of the confidence interval estimate for all American adults.