The following data represents the percentages of family income allocated to
groceries for a random sample of 50 shoppers in Windhoek.
Percentages of family income Number of shoppers
10-<20 14
20-<30 6
30-<40 16
40-<50 3
50-<60 11
Construct a 99% confidence interval for the actual mean percentages of family
income allocated to groceries in Windhoek.