8 3 A number of new techniques for teaching reading have been proposed in the educational literature A researcher designs the following study to evaluate three of these new methods along with the standard method which has been used for a number of years In a large school district five elementary schools are selected for inclusion in the study Four third grade teachers are ran domly selected in each of the five schools and the four reading techniques are randomly assigned to the teachers The teachers participate in a 2 week workshop to learn the fine points of their assigned technique The students in the 20 classrooms are given a standardized reading examina tion at the end of the semester with the average score in each classroom used as the measure of the effectiveness of the teaching technique Thus there are five measurements of the effective ness of each of the four teaching techniques a What are the populations of interest in this study b The conclusions of this study can properly be inferred for what populations c Would it be appropriate to use the AOV F test to evaluate whether there is a difference in the average scores of the four teaching techniques 8 4 In Example 8 3 suppose the organization wanted to compare the mean test scores of Catho lic priests and Methodist ministers Note that it appears based on the data that these two groups have the same variance What is the gain in using a two sample t test having sy in the denomina tor as opposed to using the conventional pooled t test with s2 the average of the sample variances for the Catholic priests and Methodist ministers