For Exercises 8.1 and 8.2, see page 419; for 8.3 and 8.4, see page 421; for 8.5 to 8.7, see page 423; for 8.8 to 8.11, see pages 425426; for 8.12, see page 426; for 8.13 and 8.14, see page 429; and for 8.15 and 8.16, see page 431.

Question 8.9

8.9 What does the confidence interval tell us

Inspect the outputs in Figure 8.3, and report the confidence interval for the percent of people who would get better sun protection from your product than from your competitor's. Be sure to convert from proportions to percents and round appropriately. Interpret the confidence interval and compare this way of analyzing data with the significance test.

426

8.9

(44.1%, 85.9%). With 95% confidence, the percent of people who would get better protection from your product is between 44.1% and 85.9%. The confidence interval gives similar information to the significance test that the percentage is not significantly different than 50% because 50% is inside our interval.