Statistics for Big Data For Dummies
Book image
Explore Book Buy On Amazon

When designing a study, the sample size is an important consideration because the larger the sample size, the more data you have and the more precise your results will be (assuming high-quality data). If you know the level of precision you want (that is, your desired margin of error), you can calculate the sample size needed to achieve it.

To find the sample size needed to estimate a population mean,


or a population proportion (p), use the following formula:


where z* is the critical value for the confidence level you need; MOE represents the desired margin of error; and


represents the population standard deviation.



σ is unknown,

  • When looking for




    with the sample standard deviation, s, from a pilot study.

  • When looking for p, estimate


    with p0(1 – p0), where p0 is some initial guess (usually 0.50) at p.

About This Article

This article is from the book:

About the book authors:

Alan Anderson, PhD, is a professor of economics and finance at Fordham University and New York University. He's a veteran economist, risk manager, and fixed income analyst. David Semmelroth is an experienced data analyst, trainer, and statistics instructor who consults on customer databases and database marketing.

This article can be found in the category: