4. Some psychologists have suggested that teachers’ expectancies influence intellectual functioning. The file VIQ.dat contains pretest verbal IQ scores for students in grades 1 and 2 who were assigned to one of three ability tracks. (The data are from Elashoff and Snow, 1970, and originally collected by R. Rosenthal. See Section 1.8 on how to obtain these data.) The experimental group consisted of children for whom positive expectancies had been suggested to teachers. Compare the trimmed means of the control group to the experimental group, taking into account grade and tracking ability. When examining tracking ability, combine ability levels 2 and 3 into one category, so a 2-by-2-by-2 design is used.