Sample Size Calculation
Evaluation of the necessary sample size to ensure statistically valid results, considering the study type, the main variable, the significance level, and the desired power. Ideal for projects in the planning stage.
What it is
A sample size calculation matched to your study design: cross-sectional, cohort, clinical trial or repeated measures.
We set the significance level (α), the statistical power (1−β) and the expected effect size, and adjust for attrition, non-response and eligibility criteria. It is best done while you write the protocol, before collecting any data.
What's included
- Design around your objectivesWe choose the calculation that fits your objective and your type of study.
- ParametersThe significance level (α), the power (1−β) and the expected effect size.
- AdjustmentsAttrition, non-response and eligibility criteria, built into the final number.
- TraceabilityThe formula, the software and the references, documented at every step.
- Email supportPersonalized help while you set up your study.
What you receive
- Technical reportPDFThe calculation step by step, with the final sample size.
- Parameter reportEvery input value, listed so a committee can check it.
- Sensitivity analysis (optional)How the sample size changes across power levels or margins of error.
- Materials and Methods templateText ready to adapt to your protocol or manuscript.
Frequently asked questions
Why does sample size matter?
A sample that is too small can miss a real effect, and one that is too large wastes resources. The calculation keeps your study valid and efficient.
What information do you need from me?
Your objective and study design, plus an estimate of the variability and of the effect you expect to find, from pilot data or from the literature.
What are power and alpha?
Power is the chance of detecting a real effect, usually set at 80% or 90%. Alpha is the chance of a false positive, usually 0.05.
Do ethics committees ask for it?
Usually yes. The report documents the formula, the software and the references, so you can attach it to your protocol.
Tell us about your study
We reply with questions and a quote.