On a Chilly Spring Afternoon, 10 Lab Sections of a Statistics

Short Answer

On a chilly spring afternoon, 10 lab sections of a statistics class all have full attendance. The 10 lab sections each have the same number of students attending. A survey is about to be administered to a sample of the students. It has been decided to first randomly select 3 of the 10 lab sections and then give the evaluation to a simple random sample of 25% of the students in those selected lab sections. What sampling technique is being used for this survey?