1. A random sample of 100 households' weekly food expenditure represented by x from a particular city gave the following statistics:
xi = 11,000, and xi2 = 1,900,000.
(a) Find the mean and standard deviation for these data.
(b) Assuming that the food expenditure of the households of an entire city of 400,000 will have a bell-shaped distribution, how many households of this city would you expect to fall in each of the intervals, x ± s, x ± 2s, and x ± 3s?