According to the Census Bureau, 3.21 people reside in the typical American household. A sample of 25 households in Arizona retirement communities showed the mean number of residents per household was 2.74 residents. The standard deviation of this sample was 1.35 residents. At the .05 significance level, is it reasonable to conclude the mean number of residents in the retirement community household is less than 3.21 persons?
State the decision rule for .05 significance level.