If you are learning student views about, say, an introductory math course, you could obtain information from a representative group of students or from all students in the course. If the number of students is not too large, it often is preferable to ask them all. The data collection signals to students that you are interested in their views. The more who understand this the better. However, you will have more data to analyze. In the example mentioned above, the CLIP administered a survey to all students in certain spring semester STEM courses. Follow up phone interviews and focus groups were conducted with a sample of students who volunteered to participate.