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In: Statistics and Probability

The water works commission needs to know the mean household usage of water by the residents...

The water works commission needs to know the mean household usage of water by the residents of a small town in gallons per day. Assume that the population standard deviation is 2.3 gallons. The mean water usage per family was found to be 20.5 gallons per day for a sample of 1559 families. Construct the 90% confidence interval for the mean usage of water. Round your answers to one decimal place.

lower endpoint = ?

upper endpoint =?

Solutions

Expert Solution

Solution :

Given that,

= 20.5

= 2.3

n = 1559

At 90% confidence level the z is ,

= 1 - 90% = 1 - 0.90 = 0.10

/ 2 = 0.10 / 2 = 0.05

Z/2 = Z0.05 = 1.645

Margin of error = E = Z/2* (/n)

= 1.960 * (2.3 / 1559)

= 0.1

At 90% confidence interval estimate of the population mean is,

- E < < + E

20.5 - 0.1< < 20.5 + 0.1

20.4 < < 20.6

lower endpoint = 20.4

upper endpoint = 20.6

orchestra answered 3 years ago
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