Lecturers for IOP2601 are interested to know whether there is a relationship in the performance of students on assignments during the semester and the exams at the end of the semester. As part of data collection, the lecturers selected 100 students out of the 547 students registered for the module. In the selection of students to be included in the study, they made sure different levels of performance were represented [from below average to above average]. The type of research that will be conducted by the lecturers would be classified as ________