In Example 7.5 we calculated a 95% confidence interval estimate of the Healthy Eating Index-2005 score for a random sample of participants at the time of their first interview. Recall that there are two observations for each person in the study. The first observation, identified by daycode = 1, contains data from the first interview and the second observation, daycode = 2, contains data from the second interview. Find a 95% confidence interval for the mean HEI-2005 score for participants at the time of their second interview. The data are stored in the data file HEI Cost Data Variable Subset.
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