The random sample of n550 male adults in Example 8.6 had an average of 756 grams of dairy products per day, with a sample standard deviation of 35 grams. Find an approximate 95% confidence interval for m, the average daily intake of dairy products for all male adults.

1. Select Stat ➤ Basic Statistics ➤ 1-Sample Z and select Summarized data in the top drop-down list in Figure 8.12(a). Enter the values for n and x in the appropriate boxes and enter the value for s535 in the box marked “Known standard deviation.” (Notice that we are assuming that the population standard deviation, s, can be approximated by s.)

2. The Options dialog box will allow you to change the confidence level from the default of 95% to another level if necessary. The resulting confidence interval (743.25, 768.75)
is shown in Figure 8.12(b).