The positive effect of water fluoridation on dental health is well documented. One study that validates this is described in the article “Impact of Water Fluoridation on Children’s Dental Health: A Controlled Study of Two Pennsylvania Communities” (American Statistical Association Proceedings of the Social Statistics Section : 262– 265). Two communities were compared. One had adopted fluoridation in 1966, whereas the other had no such program. Of 143 randomly selected children from the town without fluoridated water, 106 had decayed teeth, and 67 of 119 randomly selected children from the town with fluoridated water had decayed teeth. Let p1 denote proportion of all children in the community with fluoridated water who have decayed teeth, and let p2 denote the analogous proportion for children in the community with unfluoridated water. Estimate p1 = p2 using a 90% confidence interval. Does the interval contain 0? Interpret the interval.
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