The American Water Works Association reports that the per capita water use in a single- family home is 69 gallons per day. Legacy Ranch is a relatively new housing development. The builders installed more efficient water fixtures, such as low-flush toilets, and subsequently conducted a survey of the residences. Thirty-six owners responded, and the sample mean water use per day was 64 gallons with a standard deviation of 8.8 gallons per day. Required:
a. At the 0.10 level of significance, is that enough evidence to conclude that residents of Legacy Ranch use less water on average?
b. What is the decision rule?