The U.S. Census Bureau reports family incomes on a yearly basis. Incomes increased between 2005 and 2010. The data that arise from samples from these years are given in a file titled Incomes.
a. Determine if the income of families in the United States in 2005 to 2010 had different standard deviations. Use a significance level of 0.05.
b. Would it be valid to use a two-sample t -test on these data to determine if the average of incomes of U.S. families was different between 2005 and 2010? Explain.