Empirical surveys are an indispensable tool in sociology, psychology, medical research, consumer studies and a wide range of other disciplines and professions. In such surveys, a sample population is queried or studied and the results are used to extrapolate conclusions about the population at large. Some studies are nonrandomized, meaning that the survey population was chosen not at random, but according to more selective (or self-selective) criteria. You can calculate sample size for such studies with the formula n = N / (1+N(e^2)), where n is the sample size, N is the population size and e is the degree of precision.
Instructions
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Input the value for N, which is simply the overall population size from which you will draw a sample.
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Calculate e, the degree of precision desired by the study. This typically appears in published surveys as "margin of error," and can range from 0 to 100 percent, but values between 1 and 5 percent are more typical, depending on the nature of the study.
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Calculate the sample size according to the formula. For example, if your overall population size is 10,000, and you seek a sample that will give you a degree of precision of 3 percent, then you would compute n = 10,000 / (1+ 10,000(.03)^2), which yields a sample size of 1,111.