A city planner wants to estimate the average monthly residential water usage in

Question

A city planner wants to estimate the average monthly residential water usage in the city. He selected a random sample of 39 households from the city, which gave the mean water usage to be 3411.60 gallons over a one-month period. Based on earlier data, the population standard deviation of the monthly residential water usage in this city is 387.30 gallons. Make a 97% confidence interval for the average monthly residential water usage for all households in this city. Round your answers to two decimal places. to gallons Click if you would like to Show Work for this question: Open Show Work

Explanation / Answer

mean is 3411.60 ans s is 387.3

standard error for sample size 39 is SE=s/sqr(N)= 387.3/sqrt(39)=62.0176

z for 97% confidence is 2.17

lower bound is 3411.60-2.17*62.0176=3277.02

upper bound is  3411.60+2.17*62.0176=3546.18

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