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 . We will treat these data as an SRS from a Normally distributed population with standard deviation .

  1. (a) Give a 95% confidence interval for the mean holiday spending estimate based on these data.

  2. (b) The mean holiday spending estimate of included 12% of respondents who answered “No opinion.” This group includes those respondents who do not celebrate Christmas and thus reported $0. Do you trust the interval you computed in part (a) as a 95% confidence interval for the mean holiday spending estimate for all American adults? Why or why not?