External validity Articles — Atticus Li

Atticus Li

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External validity

Articles exploring external validity through the lens of behavioral science and experimentation. Practical frameworks for growth leaders who measure in revenue, not vanity metrics.

2 articles

external validity Mar 27, 2026 7 min read

External Validity Threats: Why Your A/B Test Results Might Not Generalize

Discover the external validity threats that can invalidate your A/B test results, from seasonality and sample pollution to the flicker effect, and how to mitigate them.

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novelty effect Mar 27, 2026 8 min read

The Novelty Effect: Why Your A/B Test Winner Might Be Temporary

How the novelty effect inflates early A/B test results, why visual changes attract temporary attention, and how to distinguish genuine improvements from short-lived spikes.

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