Online tools

Sample size calculators

These simple tools may be useful, and indeed have been used, in a wide range of common clinical research problems. They have been thoroughly tested and we are sincerely convinced that they produce accurate results, given their input. We cannot, however, guarantee that these results will fit your particular purpose. Their use should be guided by sound clinical and methodological judgment.

Please feel free to contact us for any question or remark concerning these tools. We shall also gladly help if your project’s requirements are beyond the scope of these simple tools.

Please be aware, that planning the right sample size for a given study usually entails more than a mere calculation. Particular attention should be paid to the strength of the hypotheses underlying the calculation and to other issues such as recruitment or attrition rates. Sample size determination may also be rendered more complex by stratification, multiple analyses or other design sophistications.

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