Number of Pupils in a Class A large school district has several middle schools. Three schools were randomly chosen, and four classes were selected from each. The numbers of pupils in each class are shown here. At = 0.10 , is there sufficient evidence that the mean number of students per class differs among schools? Use the P -value method with a graphing calculator. Assume that all variables are normally distributed, that the samples are independent, that the population variances are equal, and that the samples are simple random samples, one from each of the populations. .