During the winter of 2008-2009, the average utility bill for residents of a cert

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

The statistical software output for this problem is:

One sample T summary hypothesis test:
: Mean of population
H0 : = 191
HA : < 191

Hypothesis test results:

Hence,

a) Critical value = -1.671

Test statistic = -3.02

Conclusion: Option A is correct.

b) Option C is correct.

c) P - value = 0.002

Mean Sample Mean Std. Err. DF T-Stat P-value 182.49 2.8156589 59 -3.0223832 0.0019

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