In an effort to reduce energy costs, a major university has installed more effic

Question

In an effort to reduce energy costs, a major university has installed more efficient lights as well as automatic sensors that turn the lights off when no movement is present in a room. Historically, the cost of lighting an average classroom for 1 week has been $265. To determine whether the changes have signficantly reduced costs, the university takes a sample of 50 classrooms. They find that the average cost for 1 week is $247 with a standard deviation of $60. When testing the hypothesis (at the 5% level of significance) that the average energy use has decreased from the past, what is the p-value? (please round your answer to 4 decimal places)

Explanation / Answer

X- cost of lighting a room

mu = 265

n = sample size = 50

x bar = 247

x bar - mu = -18

s= 60

Std error = 60/ rt 50 = 8.485

H0: mu = 265

Ha: mu < 265

left tailed test

z = mean diff/std error = -18/8.485

=-2.121

p value = 0.016961.

= 0.0170

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