Land's bend sells a wide variety of outdoor equipment and clothing. the company sells both through mail order and via the internet. random samples of sales receipts were studied for mail-order sales and internet sales, with the total purchase being recorded for each sale. a random sample of 17 sales receipts for mail-order sales results in a mean sale amount of $67.70 with a standard deviation of $23.75. a random sample of 10 sales receipts for internet sales results in a mean sale amount of $60.80 with a standard deviation of $29.25. using this data, find the 80% confidence interval for the true mean difference between the mean amount of mail-order purchases and the mean amount of internet purchases. assume that the population variances are not equal and that the two populations are normally distributed. step 1 of 3 : find the point estimate that should be used in constructing the confidence interval.