Goran is teaching a math course to incoming students. He is interested in comparing his effectiveness teaching this course using activity-based learning to his effectiveness teaching this course using textbook presentation. He gives each of his students a pretest and forms two groups of students each. To help make sure that the groups are similar in composition with respect to factors such as age, math ability, and test anxiety, the students are randomly assigned into the two groups. One of the two groups is randomly assigned to be taught by Goran using the activity-based learning approach for the duration of the course, and the other group will be taught by Goran using textbook presentation for the duration of the course. At the end of the course, Goran will test all of the students again with a posttest, and he will examine the increase in test score from the pretest to the posttest for each group. (a)First choose whether the procedure described above is an observational study or a designed experiment. Then further categorize the procedure by choosing the correct type of observational study or designed experiment. Observational study Designed experiment prospective double-blind retrospective completely randomized