How much should be the margin of error or confidence interval for a PhD research when the population is around 950 and the respondent types are CEO/CTO/CMO/CFO/COO?
Well the margin of error is sort of up to you. Here is how I would choose the sample size for a simple random sample from this population. Let N=950. suppose p=#CEO/n, then q=1-p=fract. of non-CEOs in a sample of size n.. The worst margin of error you get(i.e. the largest sample size you would get) is when p=q=0.5 so the sample size n=(Npq)/[(N-1)D+pq] where D=(B^2)/4. Now you know everything but B which is the bound on the error of estimation. Since I don't know if you are asking Likert scale questions or ???. I will suggest B=0.05. However this is up to you. How close do you want to estimate the population p? All of this is in Scheaffer et al, Elementary Survey Sampling, 5th ed., Duxbury, sect. 4.5. Hope this helps.
Dear RG colleague,
Determining the sample sizes involve resource and statistical issues. Usually, researchers regard 100 participants as the minimum sample size when the population is large. However, In most studies the sample size is determined effectively by two factors: (1) the nature of data analysis proposed and (2) estimated response rate.
For example, if you plan to use a linear regression a sample size of 50+ 8K is required, where K is the number of predictors. Some researchers believes it is desirable to have at least 10 respondents for each item being tested in a factor analysis, Further, up to 300 responses is not unusual for Likert scale development according to other researchers.
Another method of calculating the required sample size is using the Power and Sample size program (www.power-analysis.com).
Regards,
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