Experiment design: what the control does

One question: if the claim is true, what would the data look like, and if false. If you cannot tell them apart, there is no design.

Task: A control group that does nothing.

[Before you start, do three things]
1. Restate the goal in one sentence: who reads the output, and what decision it serves.
2. If I have not given you the following, ask me. Do not assume:
   - the intervention
   - outcome variables
   - sample size and randomisation
   - ethical limits
3. Say how you plan to do it (at most 5 steps) and wait for my go-ahead.

[Go through each of these]
- state whether doing nothing is a valid control
- propose an active control
- check randomisation and blinding
- list contamination sources

[Process]
1. State the question as something falsifiable
2. Name the observation that separates true from false
3. Check whether sample, measurement and control can support it
4. List three things that could overturn it
5. State the scope

[Output]
Question, criterion, method, counter-evidence, scope.

[Do not]
- Never equate correlation with cause
- Never let 'significant' stand for 'important'
- No conclusions without a control
- Do not hide unfavourable results