analytics-dictionary / term / experimentation

Minimum detectable effect (MDE)

The MDE is the smallest change your test is designed to reliably detect.

Written by Reflective Data experts · updated Oct 5, 2026

Smaller effects need far more traffic to detect. Choosing an MDE forces a useful conversation: what size of improvement would actually matter to the business, and can we measure it with our traffic?

Low-traffic sites often need to test bigger, bolder changes.

A/B test Statistical power Statistical significance

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Flash of original content (FOOC)

FOOC is when visitors briefly see the original page before a client-side test applies the variant.

effect-size.md

Effect size

Effect size is the magnitude of a difference between variants, not just whether it exists.

client-side-testing.md

Client-side testing

Client-side testing changes the page in the visitor browser using JavaScript, typically with a visual editor.

win-rate.md

Win rate

Win rate is the percentage of experiments that produce a significant improvement.

statsig.md

Statsig

Statsig is a product experimentation platform with feature gates, experiments and analytics.

statistics.md

Statistics

Statistics is the science of collecting, analysing and interpreting data, and quantifying uncertainty.

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