Sample Size Formulas for our Sample Size Calculator

Here are the formulas used in our Sample Size Calculator:

Sample Size

ss = Z 2 * (p) * (1-p)

c 2

Where:

Z = Z value (e.g. 1.96 for 95% confidence level)
p = percentage picking a choice, expressed as decimal
(.5 used for sample size needed)
c = confidence interval, expressed as decimal
(e.g., .04 = 4)


Correction for Finite Population

ss

new ss =
1+ ss-1

pop


Where: pop = population

Research Aids

Research Aids
"Best Survey Software"
TopTenReviews selected The Survey System as the Best Survey Software.
"The Survey System gains our highest marks for survey creation, analysis and administration methods, making it the best survey software in our ranking... This is the only product in our lineup that offers all features and tools we considered. For these reasons, The Survey System earns our TopTenREVIEWS Gold Award." Read More