In preparing for a test on a set of material, is it better to study one topic at a time or to study topics mixed together? in one study,1 a sample of fourth graders were taught four equations. half of the children learned by studying repeated examples of one equation at a time, while the other half studied mixed problem sets that included examples of all four types of calculations grouped together. a day later, all the students were given a test on the material. the students in the mixed practice group had an average grade of 77 , while the students in the one-at-a-time group had an average grade of 38 . what is the best estimate for the difference in the average grade between fourth-grade students who study mixed problems and those who study each equation independently?