A researcher is interested in determining whether test performance of students can be improved by ...

A researcher is interested in determining whether test performance of students can be improved by providing them with individual tutoring. The researcher randomly divides fifty first-year college students into two groups. In Group A, the instructor lectures to them for three hours per week. Group B receives an equal amount of lecturing, but their instructor also meets with each student for thirty minutes every week. Each group takes the same final exam. The test performance of students in Group B is about the same as that of students in Group A. This study is an example of a(n) ____.
 
  a. correlational study
  b. case study
  c. experiment
  d. survey