Hollow is proud of their energy saving program. A sample of 40 houses reveals an
ID: 3267137 • Letter: H
Question
Hollow is proud of their energy saving program. A sample of 40 houses reveals an average saving of 47.5 kilowatt hours per week with a standard deviation of 55. Find the t score for a 90% confidence limit. Calculate 90% confidencw limit around your best estimate of the average savings. Hollow is proud of their energy saving program. A sample of 40 houses reveals an average saving of 47.5 kilowatt hours per week with a standard deviation of 55. Find the t score for a 90% confidence limit. Calculate 90% confidencw limit around your best estimate of the average savings.Explanation / Answer
From information given, xbar=47.5, s=55, n=40, where, xbar is sample mean, and s is sample standard deviation. The population standrad deviation is unknown and sample size is large, therefore, use Student's t distribution to compute t interval for mu.
Therefore, 90% confidence interval for population mean energy savings is as follow:
xbar+-talpha/2 (s/sqrt n), where, t alpha/2 denotes t critical at alpha/2 (alpha=0.10) and n-1 degrees of freedom, n is sample size.
=47.5+-2.0227(55/sqrt 40)
=(29.91,65.09)
One can be 90% confident that the true population mean energy savings per week is beteen 29.91 Kilowatt hours and 65.09 Kilowatt hours.
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