Astatistics teacher conducted an experiment to test whether the use of a new review booklet will improve her students' semester grades. the teacher randomly selected 20 students from her class and assigned the new review booklet to 10 of the students. the remaining 10 students did not use any review material. at the end of the semester, the teacher reviewed the students' semester grades. the semester grades of the students who used the new review booklet were the same as the semester grades of the students who did not. what can be concluded from the teacher's observations? a. it can be concluded that the new review booklet does not improve students' semester grades. b. it can be concluded that the new review booklet reduces students' semester grades. c. there is not enough information to make any conclusions regarding the new review booklet. d. it can be concluded that the new review booklet improves students' semester grades.