During the winter of 2008-2009, the average utility bill for residents of a cert
ID: 3316686 • Letter: D
Question
During the winter of 2008-2009, the average utility bill for residents of a certain state was $191 per month. A random sample of 60 customers was selected during the winter of 2009-2010, and the average bill was found to be $182.49 with a sample standard deviation of $21.81. Complete parts a and b below. a Using -0.05, does this sample provide enough evidence to conclude that the average utility bill in this state was lower in the Determine the hypotheses O A. Hus 191 and HIP 191 O B. Ho: 2191 and H1:Explanation / Answer
a. Pop. Mean = 191
n = 60
Sample Mean = 182.49
sample deviation = 21.81
a. alpha = .05
B is the right option as the null hypothesis has an inequality, lower side
B. Ho: Mu > = 191, Mu < 191
The critical value is +/- 1.96
p-value is t = (182.49-191)/(21.81/sqrt(60)) = -3.02
The P-Value is .003732.
The result is significant at p < .05.
In terms of Z , -3.02 is less than -1.96 ,i.e in the rejection region
The conclusion is : Reject Ho: There is sufficient evidence to conclude that the average ultility bill in this state was lower in the winter of 20090-10 than it was in the winter of 2008-09
b. Even when you decrease it to .01, we will still reject Ho since p-value<.01
Option D is right option
c. The P-Value is .003732.
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