Here is an example of how the math works assuming you chose a 90 confidence level 6 standard deviation and a margin of error confidence interval of - 4. The standard formula for sample size is. If you have a small to moderate population and know all of the key values you should use the standard formula.
Further information can be found in this article.
Plug in your Z-score standard of deviation and confidence interval into the sample size calculator or use this sample size formula to work it out yourself. For a confidence level of 95 a is 005 and the critical value is 196 MOE is the margin of error p is the sample proportion and N is the population size. 21 - Sample Size for Estimating Population Mean and Total How large is a sample size that is large enough for estimating the population mean. There are no specific sample size formulas or calculations for qualitative sample sizes.