Best Test

Two plausible options depend on different assumptions, and talking no longer helps. Find the cheapest real observation on which those options would lead you to expect different results.

Two predictions. One separating observation. Then decide.

Identify the uncertainty that separates the leading options. Write what you would expect to observe if each option’s assumptions were right, then choose a small real-world observation that distinguishes them. Set an interpretation rule before looking; a test that both options pass cannot settle their difference.

Try this when…

We are arguing about an assumption we could check.

Both options sound good in a presentation.

The proposed trial would make either option look successful.

One missing fact keeps changing our preferred choice.

What you can use it for

Choosing designs

Test a task where the leading designs make different usability predictions.

Selecting an approach

Find whether the constraint is the one each intervention assumes.

Resolving demand uncertainty

Observe real behavior at a decision point rather than relying only on opinions.