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REVIEW QUESTIONS AND EXERCISES 207 22. Determinations of saliva pH levels were made in two independent random samples of seventh-grade schoolchildren. Sample A children were caries-free while sample B children had a high incidence of caries. The results were as follows: A: 7.14, 7.11, 7.61, 7.98, 7.21, 7.16, 7.89 B: 7.36, 7.04, 7.19, 7.41, 7.10, 7.15, 7.36. 7.24. 7.86. 7.47. 7.82, 7.37. 7.66. 7.62, 7.65 7.57. 7.64, 7.00. 7.25, 7.19 Construct a 90 percent confidence interval for the difference between the population means, Assume that the population variances are equal