When you want a relatively (e.g., the estimate that 75% of teachers support a policy plus or minus 4% is more narrow than an estimate of 75% plus or minus 5%).
When you expect a or a .
When you use a of random sampling (e.g., cluster sampling is less efficient than proportional stratified sampling).
When you expect to have a . The response rate is the percentage of people in your sample who agree to be in your study.
Sampling in Qualitative Research
Sampling in research is usually (see the above discussion of purposive sampling). The primary goal in qualitative research is to select information rich cases.
There are several specific purposive sampling techniques that are used in qualitative research:
(i.e., you select a wide range of cases).
(i.e., you select a small and homogeneous case or set of cases for intensive study).
(i.e., you select cases that represent the extremes on some dimension).
(i.e., you select typical or average cases).
(i.e., you select cases that are known to be very important).
(i.e., you purposively select cases that disconfirm your generalizations, so that you can make sure that you are not just selectively finding cases to support your personal theory).
(i.e., you select useful cases as the opportunity arises).
(i.e., you mix the sampling strategies we have discussed into more complex designs tailored to your needs).
Sampling in Mixed Research