Here's a simple handout on the types of sampling strategies and their advantages and disadvantages that can be helpful: http://www2.hawaii.edu/~cheang/Sampling%20Strategies%20and%20their%20Advantages%20and%20Disadvantages.htm

Best regards,

Debra

It is almost going to have to be a convenience sample consisting of the groups of students and instructors willing to let you give your survey in their classes.

It depends on the kind of the sample and the willingness of the selected participants to cooperate.

You need to do systematic random sampling.

But in some cases, my colleague, Abdullah Noori , and to fit the purposes of the research, researchers don't select their sample randomly.

Let us assume that a university consists of 3 major faculties: humanitarian, natural sciences, and physical sciences. A representative sample will be expected to include a number of students & instructors from each of these faculties (say 20) ending up with a total of 60 participants.

Of course, the researcher will consult them personally and they will be free to agree or to disagree about participation. Here, the power of convincing these persons "about the importance or the significance of their responses" will play a key role. Promising them of small number of short questions can help a lot.

Please do not be disappointed if the number of participants is reduced to half of what you expected. Still, a number of 30 is good for research if it is properly designed & if it is well analyzed.

You might be allowed to interact with some of them through skype, perhaps participating in the activities there or guiding the activity and asking them to finally answer a survey. Teaching English allows you to contact with students from different faculties as they are enrolled in the same English course.

Sample can be selected by using any of sample and sampling techniques such as simple random sampling techniques, purposive sampling techniques, stratifying sample techniques, snow bolling and others, when we are dealing with large populations we can use descriptive research of the survey type through questionnaire.