Total Sampling Size for Stratified Sampling

Question

Hi!

I have an undergraduate mixed-method thesis and my sampling technique is disproportionate stratified sampling technique. My strata are students and faculty members. The population of students is 1200 while faculty members is 30. My study is only limited to my department.

My question: Before I divide my strata, I need a total sample size first. I am seeing a lot of total sample size formula in the internet and I'm not sure what to use. Could you suggest to me the best formula of total sample size I can use?

Thank you!

Answer 1

Hi Jared,

In general, sample size should be no greater than 10% of the population. If you are treating your population as the 1200 students, your sample size should be 120 or less—100 could also work. The only sample size formula I know depends on desired margin of error. N =(z*/m)²*p*q, where z* is a critical value, m is margin of error, p is the probability estimate, q is 1-p. I don’t know if that works for stratification, though. Based on my limited knowledge, I suggest a total sample size of 100-120, strata of about 20 per group.