A real estate office wants to make a survey in a certain town, which has 50,000 households, to determine how far the head of household has to commute...

A real estate office wants to make a survey in a certain town, which has 50,000 households, to determine how far the head of household has to commute to work. A simple random sample of 1,000 households is chosen, the occupants are interviewed, and it is found that on average, the heads of the sample households commuted 8.7 miles to work; the SD of the distances was 8.90 miles.(All distances are one-way; if someone isn't working, the commute distance is defined to be 0.) Suppose 86 different survey organizations take simple random sample of 100 persons in the town. Each organization gets a 90% confidence interval. About how many of these intervals should cover the population average?