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ML Academy

Experimentation and causality

Interview question

  • midlevel
  • 10 minsuggested time
  • 2Data scientist, Data analyst

Booking conversion on the website is 5%. You want to detect an absolute lift of 0.5 percentage points (to 5.5%) with a two-sided test at alpha 0.05 and 80% power. Roughly how many users do you need per group, and what drives that number?

Tests: Power and sample-size reasoning for proportions, the role of minimum detectable effect, and practical constraints (traffic, duration, weekly cycles).

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