Question 7.31

7.31 Supermarket shoppers.

A marketing consultant observed 40 consecutive shoppers at a supermarket. One variable of interest was how much each shopper spent in the store. Here are the data (in dollars), arranged in increasing order:

shoprs

5.32 8.88 9.26 10.81 12.69 15.23 15.62 17.00
17.35 18.43 19.50 19.54 20.59 22.22 23.04 24.47
25.13 26.24 26.26 27.65 28.08 28.38 32.03 34.98
37.37 38.64 39.16 41.02 42.97 44.67 45.40 46.69
49.39 52.75 54.80 59.07 60.22 84.36 85.77 94.38
  1. Display the data using a stemplot. Make a Normal quantile plot if your software allows. The data are clearly non-Normal. In what way? Because , the procedures remain quite accurate.
  2. Calculate the mean, the standard deviation, and the standard error of the mean.
  3. Find a 95% confidence interval for the mean spending for all shoppers at this store.

7.31

(a) There are three large outliers, making the data not Normal.
(b)
(c) (27.3384, 40.9296).