Study Design and Modeling

This book is a discussion space for the study design process and the modeling choices that support it. The goal is to make product questions testable before a launch, then keep the measurement system stable enough for follow-up decisions.

Study Design Process

A study starts by defining the decision it should support. From there, the work becomes a sequence of choices: product surface, eligible population, assignment unit, primary signal, guardrails, baseline rate, and minimum detectable effect.

Good study design keeps those choices visible. It should be possible to read the plan and understand what action would follow from a positive, negative, or inconclusive result.

Modeling Frame

Modeling is useful when it clarifies uncertainty rather than hiding it. For lightweight product work, useful models often estimate:

• baseline conversion or completion rates,

• expected lift and sample size,

• traffic windows and exposure limits,

• guardrail risk,

• post-launch quality drift.

The model does not replace judgment. It gives the team a shared numerical frame for deciding whether a study is feasible and what evidence is strong enough to act on.

Continue with Experiment Design.