The average expenditure on Valentine's Day was expected to be $100.89 (USA Today, February 13, 2006). Do male and female consumers differ in amounts they spend? The average expenditure in sample survey of 40 male consumers was $135.67, and average expenditure in a sample survey of 30 female consumers was $68.64. Based upon past surveys, the standard deviation for male consumers is supposed to be $35, and the standard deviation for female consumers is supposed to be $20. The z value is 2.576 .
Round your answers to 2 decimal places.
a. Determine the point estimate of the population mean expenditure for males minus the population mean expenditure for females?
b. At 99% confidence, what is the margin of error?
c. Develop a 99% confidence interval for the mean for the males minus the mean for the females.