22. To study the effect of fluoridated water supplies on tooth decay, two communities of roughly the same socioeconomic status were chosen. One of these communities had fluoridated water while the other did not. Random samples of 200 teenagers from both communities were chosen, and the numbers of cavities they had were determined. The following data resulted.

Do these data establish, at the 5 percent level of significance, that the number of dental cavities a person has is not independent of whether that person’s water supply is fluoridated? What about at the 1 percent level?

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Cavities Fluoridated Town Nonfluoridated Town 0 154 133 1 20 18 2 14 21 3 or more 12 28