The file measles. dat contains data consistent with that obtained in a survey of par- ents whose children had not been immunized for measles during a recent campaign to immunize all children between the ages of 11 and 15. during the campaign, 7633 chil- dren from the 46 schools in the area were immunized; 9962 children whose records showed no previous immunization were not immunized. in a follow-up survey to explore why the children had not been immunized during the campaign, roberts et al. (1995) sent questionnaires to the parents of a cluster sample of the 9962 chil- dren. ten schools were randomly selected, then a sample of the mi nonimmunized children from each school was selected and the parents of those children were sent a questionnaire. not all parents responded to the questionnaire; you will examine the effects of nonresponse in exercise 13 of chapter 8.

a estimate, separately for each school, the percentage of parents who returned a consent form (variable returnf ). for this exercise, treat the "no answer" responses (value 9) as not returned.