Use the sample statistics from Exercise 30 and assume the number of households in the sample is 40.
(a) Estimate the number of households whose monthly utility bills are between $54 and $86.
(b) In a sample of 20 additional households, about how many households would you expect to have monthly utility bills between $54 and $86?
Use the Empirical Rule
Exercise 30
The mean monthly utility bill for a sample of households in a city is $70, with a standard deviation of $8. Between what two values do about 95% of the data lie? (Assume the data set has a bell-shaped distribution.)