During the winter of2008-2009, the average utility bill for residents of a certain state was $173 per month. A random sample of 30 customers was selected during the winter of2009-2010, and the average bill was found to be $163.41 with a sample standard deviation of $22.28.

a) Using alpha =0.05, does this sample provide enough evidence to conclude that the average utility bill in this state was lower in the winter of2009-2010 than it was in the winder of2008-2009?

Determine the hypotheses.