Planning balances the effect worth detecting, sample size, false-positive rate, and target power.
0% target powerα = 0
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Statistics result
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Minimum Detectable Effect. Planning starts with an effect worth detecting, a significance level, a target power, and assumptions about variation or baseline rates.
1Define the smallest meaningful effect2Set alpha, power, and allocation3Round sample requirements upward and allow for attrition
Method used
MDE=(zα+zβ)·SE, with SE determined by one-sample or equal-group design.
Effects smaller than the MDE are not impossible; the design simply has less than the selected power to detect them.
What the result cannot establish
Power is a long-run probability under the assumed effect and model. It is not a guarantee of significance, data quality, or practical importance.
Assumption: Uses a two-sided normal approximation, fixed SD, independent units, and equal group sizes where applicable.
Quick guide
How to use this calculator
Enter the observations, probabilities, model parameters, or summary statistics requested by the visible labels.
Keep every value on the same scale and confirm that the selected sampling relationship, distribution, and tail convention match the question you are investigating.
Read the result together with its assumptions and interpretation. Statistical output summarizes uncertainty under a model; it does not repair biased data or establish causation.
Calculation method
How the minimum detectable effect calculator works
MDE=(zα+zβ)·SE, with SE determined by one-sample or equal-group design.
Effects smaller than the MDE are not impossible; the design simply has less than the selected power to detect them.
Worked example
Minimum Detectable Effect example
With SD 10 and 64 observations per group, an equal-group design detects roughly a 5-unit difference at 80% power.
MDE=(zα+zβ)·SE, with SE determined by one-sample or equal-group design.
Supported inputs
Precision and limits
Model and design
Uses a two-sided normal approximation, fixed SD, independent units, and equal group sizes where applicable.
Numerical scope
Inputs use double-precision numerical methods with guarded domains. Datasets accept up to 10,000 finite plain-decimal values. Extremely large parameters or probabilities deep in a numerical tail may require specialist statistical software.
Interpretation
Effects smaller than the MDE are not impossible; the design simply has less than the selected power to detect them.
Decision boundary
The calculator does not validate how data were collected, diagnose dependence or bias, choose a scientifically meaningful effect, or replace review by a qualified statistician for consequential research, medical, regulatory, safety, or policy decisions.
Privacy
Entered values and calculated results stay in this browser and are not sent to an analytics service.
