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 7.24, 7.86, 7.47, 7.82, 7.37, 7.66, 7.62, 7.65 B: 7.36, 7.04, 7.19, 7.41, 7.10, 7.15, 7.36, 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.