Calculate the upper and lower limit for a 95% confidence interval about the mean. a family wants to reduce its expenditures for personal items like gifts, newspapers, magazines and so forth. a sample of 49 months of receipts yields a mean of $220.00 with a standard deviation of $30.00. they decide to calculate a 95% confidence interval about this mean. standard error = (standard deviation)/(square root of sample size) upper limit (dollars and cents) = lower limit (dollars and cents) =