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How to Determine your Sample Size

Are you about administering a questionnaire to your program participants? Are you wondering how many of those participants you need to respond to your program survey to be “statistically correct”? In this resource, I am creating a list that shows the sample size you should be considering for your program survey. Krejcie and Morgan in 1970 created this table for determining sample size for a given population for easy reference. But before you jump to the list, let’s clarify some basic statistical jargon.

Angela Mogadishu, the Monitoring and Evaluation Officer at Madagascar Foundation, found out, from the attendant’s register that 2,800 young women attended their 5-day Women Empowerment Bootcamp (WEB). Angela designed a questionnaire to help the Foundation understand the perception of the women that attended WEB. As usual, Angela could not reach out to all the 2,800 young women that attended WEB, so she needed a certain proportion that could represent all the other women. To have a representative statistical sample, Angela chose 350 after referring to the list below. Thus the 2,800 young women are referred to as the population, while the 350 women are the sample size that should actually respond to the questionnaire she has designed. 

Wait a minute, a quick look at a population of 2,800 in the list below resulted in a sample size of 338. Why did Angela choose 350? In real-world evaluation, Angela might not get response from all the 338 because of several reasons. So she already assumed she would not get responses from 12 young women that were part of the WEB program. If I were Angela, I would target 360 respondents. Nevertheless, we can all be Angela! 

Table for Determining Sample Size for a Finite Population

PopulationSample sizePopulationSample SizePopulationSample Size
10102201401200291
15142301441300297
20192401481400302
25242501521500306
30282601551600310
35322701591700313
40362801621800317
45402901651900320
50443001692000322
55483201752200327
60523401812400331
65563601862600335
70593801912800338
75634001963000341
80664202013500346
85704402054000351
90734602104500354
95764802145000357
100805002176000361
110865502267000364
120926002348000367
130976502429000368
14010370024810000370
15010875025415000375
16011380026020000377
17011885026530000379
18012390026940000380
19012795027450000381
200132100027875000382
21013611002851000000384
Source: Krejcie and Morgan, (1970) Determining Sample Size for Research Activities. Educational and Psychological Measurement


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