Agroup educators want to determine how effective tutoring is in raising students' grades in a math class, so they arrange free tutoring for those who want it. then they compare final exam grades for the group that took advantage of the tutoring and the group that did not. suppose the group participating in the tutoring ended to receive higher grades on the exam. does that show that the tutoring worked? if not, explain why not and suggest a confounding variable.
choose the correct answer below.
a. the study shows that the tutoring worked.
b. because this was an observational study. if only shows an association. it does not show that the tutoring worked it could be that more motivated students attended the tutoring and that was what caused the higher grades.
c. because this was an observational study. it only shows an association. it does not show that the tutoring worked. it could be that an insufficient number of students were studied to show that the tutoring worked.