A National Retail Foundation survey found households intended to spend an average of $649 during the December holiday season. The survey included 600 households and the sample standard deviation was $175. The 95% confidence interval for the mean amount spent during the December holiday season is {635, 663} The prior year, the population mean expenditure per household was $632. Does your confidence interval provide evidence that the average has changed?
Yes, the confidence interval provides evidence that the average has changed. The prior year’s population mean expenditure per household, $632, is not within the 95% confidence interval, (635, 663).
