Can Slovin’s formula be used to compute for the appropriate sample size when a quota sampling is employed in the study? From what I understand, non probability sampling uses arbitrary number. But what if I need a basis for the sample size and not familiar enough with the population characteristics?
Dear Dannica Rose Aquino
I suggest the Slovin's Formula is given as follows: n = N/(1+Ne2), where n is the sample size, N is the population size and e is the margin of error to be decided by the researcher.
Best Regards
Dr. Fatemeh Khozaei
Hi,
If this is a qualitative study, saturation could be a good justification for the sample size. If it is a quantitative study, a simple power sample estimation can be a good justification. Dannica Rose has provided a possible formula and I think it works well too but can fit a simple random. Others use pragmatic restrictions, but this is not a strong argument.
Non-probability "selection" should be used instead of "sampling". Since this cannot be generalized, sample size has no importance in terms of representativeness.
Sample Size Rule
Sekaran (2013) wrote:
"Roscoe (1975) proposes the following rules of thumb for determining sample size:
1. Sample sizes larger than 30 and less than 500 are appropriate for most research.
2. Where samples are to be broken into sub-samples;(male/females, juniors/seniors, etc.), a minimum sample size of 30 for each category is necessary.
3. In multivariate research (including multiple regression analyses),the sample size should be several times (preferably 10 times or more) as large as the number of variables in the study.
4. For simple experimental research with tight experimental controls (matched pairs, etc.), successful research is possible with samples as small as 10 to 20 in size."
Reference
Sekaran, U., 2003. Research methods for business: A skill building approach. John Wiley & Sons.
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