Determine the sample size so that we are 95 confident that the estimate of the

These data are listed next. This is necessarily an observational study rather than a controlled experiment. There is no way that the researchers could have assigned children at random to parents in or out of lead- related occupations. Furthermore, the Exposed subjects were all chosen from the small group of children whose parents worked at one particular plant. They were not chosen from the larger population of children everywhere who might be exposed to lead as a result of their parents’ working conditions. If lead levels are unusually high in the Exposed group, it might be argued that the lead in their blood came from some source other than their parents’ place of work: from lead solder in water pipes at home, from lead-paint dust at school, from air pollution, and so on. For this reason a properly chosen control group of children is crucial to the credibility of the study. In principle, the children in the Control group should be subject to all of the same possible lead contaminants as those in the Exposed group, except for lead brought home from work by parents. In practice, the designers of this study chose to use two criteria in forming pairs: neighborhood and age. Neighborhood seems a reasonable choice because general envi- ronmental conditions, types of housing, and so on could vary greatly for children living in different neighborhoods. Controlling for age seems reasonable because lead poisoning is largely cumulative, so levels of lead might be higher in older children. Thus for each child in the Exposed group, researchers sought a paired child of the same age and living in the same neighborhood. Complete Listing of Dataset LEADKIDS Complete Listing of Dataset LEADEXP Exposed Control Diff Lead JobExp JobHyg 38 16 22 14 3 1 23 18 5 13 3 1 41 18 23 25 3 1 18 24 -6 39 2 1 37 19 18 41 3 2 36 11 25 18 3 2 23 10 13 49 3 2 6 2 15 47 29 2 2 31 16 15 16 1 2 34 18 16 38 3 3 24 18 6 23 3 3 14 13 1 37 3 3 21 19 2 62 3 3 17 10 7 24 3 3 16 16 0 45 3 3 20 16 4 39 3 3 15 24 -9 48 3 3 10 13 -3 44 3 3 45 9 36 35 3 3 39 14 25 43 3 3 22 21 1 34 3 3 35 19 16 73 3 3 49 7 42 31 2 3 48 18 30 34 2 3 44 19 25 20 2 3 35 12 23 22 2 3 43 11 32 35 2 3 39 22 17 36 1 3 34 25 9 23 1 3 13 16 -3 21 1 3 73 13 60 17 1 3 25 11 14 27 1 3 27 13 14 15 1 3 10 1 3