Getting The Sample Size. However the relationship is not linear ie doubling the sample size does not halve the confidence interval. Each of the shaded tails in the following figure has an area of 0025.
N population size e Margin of error percentage in decimal form z z-score. Although cost considerations make this impossible for large populations a census is attractive for small populations eg 200 or less. Necessary Sample Size Z-score2 StdDev1-StdDev margin of error2 Here is how the math works assuming you chose a 95 confidence level 5 standard deviation and a margin of error confidence interval of - 5.
If your population is less than 100 then you really need to survey all of them.
Sample Size The larger your sample size the more sure you can be that their answers truly reflect the population. N population size e Margin of error percentage in decimal form z z-score. 258 2 05 1-05 001 2 665605 0500001 16641 The sample size for the chosen parameters should be 16641 which is a very large sample. One approach is to use the entire population as the sample.
