AtheneaLab

Sample size calculation

Before collecting data, it helps to know how many people you need. Here we explain what it involves and give you calculators to do it.

What does calculating the sample mean?

It is almost never possible to study everyone you are interested in. That is why we work with a sample: a smaller group that represents that population.

Calculating the sample means estimating how many people you need for your results to be reliable. If the sample is too small, your conclusions may be imprecise or miss an effect that does exist. If it is larger than necessary, you spend extra time and resources.

What does it involve?

It depends on what you want to do with your data. There are two paths:

  • By precision. If you want to describe a population (for example, what percentage holds an opinion), the sample depends on the population size, the confidence level and the margin of error you accept.
  • By statistical power. If you want to test a hypothesis (compare groups or relate variables), the sample depends on the effect size you expect, the significance level (α) and the power you aim for, usually 0.80.

Choose your calculator

Sample size

For surveys and descriptive studies. Enter the population, the confidence level and the margin of error.

Calculate sample size

Statistical power

For hypothesis tests: correlation, Student's t, one-way ANOVA and multiple linear regression.

Calculate power

Sample for SEM

For structural equation models: with latent variables, questionnaires and relationships among several variables at once.

Calculate sample for SEM

How to cite this tool

AtheneaLab. (2026). Sample size calculation [Web application]. https://athenealab.com/en/sample-size/

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