Answer Happy

e u 8.42 Buy It Now Example 9 mentioned closing prices for list. TRY ings of the iPhone 5s on eBay. If you don't feel comfort- able bidding (or can't wait until a listing has ended), you can often purchase the item right away at the indicated Buy It Now price. A random sample of Buy It Now prices for an unlocked 16GB iPhone 5s in July 2014 showed the following prices (in S), with dot plot and box plot shown in the figure: 618,650, 608,634, 675, 618, 625, 619.630. re 600 610 620 630 640 650 660 670 680 Buy It Now Price *

a. What must we assume to use these data to find a 95% confidence interval for the mean Buy It Now price on eBay? Do these assumptions seem plausible? b. The table shows the way many statistical software packages report results. How was the standard error of the mean (SE Mean) obtained? me Variable N Mean StDev SE Mean Buy ItNow 9 630.78 20.47 6.82 958 CI (615.04 646.52) 50,

c. Interpret the 95% confidence interval in context. d. Compared to the confidence interval (569, 599) for prkes from auctions obtained in Example 9, is there evidence that the mean price is higher when purchased as Buy It Now? Explain. e. Excluding the observation of $675, the confidence interval equals (615, 636). Does this change your answer to part d?