Sample Sizes

Determining the Appropriate Sample Size

Sample size refers to the number of respondents who complete a survey or project. The number of individuals initially asked to participate is based on the expected response rate.

To determine the appropriate sample size, locate on the chart below the size of the population in the first column and cross-reference it with the level of confidence and margin of error desired. For example, if one were interested in studying an IEEE Society with 10,000 members at a confidence level of 95% and a margin of error of +/-5%, the resulting sample size of respondents would need to be approximately 370. The sample sizes assume a randomly drawn sample.

Notice that as the population exceeds 10,000 the sample size hardly increases. Although this is contrary to common sense, this has been statistically proven and is common research procedure.

For small populations, less than 200, the general rule-of-thumb is that one needs to have at least 50% of the population respond.

SAMPLE SIZES
	95% Confidence			99% Confidence
Population Size (N)	Plus or Minus 3%	Plus or Minus 5%	Plus or Minus 10%	Plus or Minus 3%	Plus or Minus 5%	Plus or Minus 10%
500	250a	218	81	250a	250a	125
1,000	500a	278	88	500a	399	143
1,500	624	306	91	750a	460	150
2,000	696	323	92	959	498	154
4,000	788	341	94	1142	544	158
5,000	880	357	95	1347	586	161
10,000	965	370	96	1556	622	164
20,000	1,014	377	96	1687	642	165
50,000	1,045	382	96	1777	655	166
100,000	1,058	383	96	1809	659	168

Source: Rea, Louis., and Richard A. Parker. Designing and Conducting Survey Research: A Comprehensive Guide. 2nd ed. San Francisco, CA: Jossey-Bass, 1997, page 121

Sample sizes for IEEE studies

For most projects, we aim to achieve results with a confidence level of 95% and a margin of error of +/-5%. These parameters ensure results that can be used to generalize to the population and to make data-driven decisions. Typically we expect a 25% return rate when surveying members. Longer, more complicated surveys on difficult topics may have response rates below 10%, while short surveys that are on extremely interesting topics can achieve response rates as high as 40-50%. Therefore, we generally ask 1,000 - 2,000 individuals to participate in our surveys, although depending on the goals of the study, the sample sizes may vary.

top of page