Question 1

What is the minimum detectable effect (MDE)?

Accepted Answer

The MDE is the smallest relative or absolute change in conversion rate you want to detect. It directly impacts sample size: smaller effects require larger samples.

Question 2

Why does traffic split matter?

Accepted Answer

Unequal splits (e.g., 80/20) increase total sample size because the smaller group needs more observations to achieve the same statistical power.

Question 3

How is sample size calculated for proportions?

Accepted Answer

We use a two-proportion z-test formula: n = (z_α/2 + z_β)² * (p1(1-p1) + p2(1-p2)) / (p2-p1)², adjusted for unequal splits.

Sample Size · Proportions

Sensitivity (MDE lift)

Power curve