Designs an A/B test or experiment with variants, success metrics, sample size, and duration for an existing hypothesis.
SkillScore82Maintained
Automatic
◆Product Management pack
Last verified 8/18/2026
What it changes
Passed 18 of 22 test cases with the skill, and 11 of 22 without it.
Without skill50%
With skill82%
Checks it passed that the model alone missed
Includes an Overview section.
Includes a Background section.
Includes a References section.
and 9 more in the full report
7 fixed11 passed either way4 still failing0 broke
Pass-rate lift
+32 pp
Tokens
+28%
Agent turns
0%
Response time
-8%
Model gemini-3.6-flashMeasured 8/18/2026v118 of 22 cases passed with skill
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 7 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 7
Prompt
We surveyed 500 cancelled subscribers using a 5-point Likert scale and open-ended text fields asking why they left our streaming platform. Here are the raw survey response rows. Can you run a survey analysis to extract sentiment clusters and top cancellation reasons?
What was checked, without and with the skill
Checked
Without skill
With skill
States that analyzing qualitative survey responses is outside controlled experiment design scope.
Missed
Passed
Refrains from outputting an A/B experiment design spec.
Passed
Passed
case-06 · gemini-3.6-flash · 8/18/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md66 lines3 files
Experiment Design
An experiment design document defines all parameters needed to run a rigorous A/B test or controlled experiment. It ensures the team aligns on what you're testing, how you'll measure success, and how long to run the test before drawing conclusions. Good experiment design prevents common pitfalls: underpowered tests, unclear success criteria, and decisions based on noise rather than signal.
When to Use
Before launching an A/B test to validate a product change
When testing a hypothesis that requires quantitative validation
After solution design to validate assumptions before full rollout
When stakeholders want data-driven evidence for a decision
To establish a culture of experimentation and learning
When NOT to Use
The hypothesis itself is not yet articulated -> use define-hypothesis first; this skill designs the test for a claim you already have
You are analyzing a completed experiment -> use measure-experiment-results
You need the event tracking that will measure the experiment -> use measure-instrumentation-spec
You are gathering opinions rather than running a controlled test -> use measure-survey-analysis
Instructions
When asked to design an experiment, follow these steps:
Articulate the Hypothesis
Write a clear, testable hypothesis in the format: "We believe [change] for [users] will [outcome] as measured by [metric]." One hypothesis per experiment - if you're testing multiple things, run multiple experiments.
Define the Variants
Describe the control (current experience) and treatment (new experience) in sufficient detail. Include screenshots, mockups, or precise descriptions so anyone can understand what users will see.
Choose Primary and Secondary Metrics
Select one primary metric that will determine success or failure. Add 2-3 secondary metrics to understand the broader impact. Include guardrail metrics to catch unintended negative effects.
Calculate Sample Size
Determine how many users you need per variant to detect your minimum detectable effect (MDE) with statistical significance. Specify your significance level (typically 0.05) and power (typically 0.80).
Estimate Duration
Based on sample size and available traffic, calculate how long the experiment needs to run. Account for weekly patterns - avoid ending mid-week if behavior varies by day.
Design and analyze A/B tests: sample size, test duration, and statistical significance for conversion experiments. Use when setting up an A/B test, calculating sample size, designing an experiment, or analyzing results.