N m 1 m 1 N. M z a 2 2 p 1 p ϵ 2. The value of the multiplier t which is driven by both the confidence level and the sample size the standard deviation s of the original data and the sample size n used for the data collection.
If you have a small to moderate population and know all of the key values you should use the standard formula.
Confidence Interval Confidence Level. E is the margin of error. The width of a confidence interval is affected by 3 measures. The standard formula for sample size is.