Choose the Discriminating Probe
Gather the evidence that best separates the remaining causes, not simply the evidence that is easiest to collect.
The question
Which observation would eliminate the most possibilities?
Do this
- Keep a list of causes consistent with all evidence so far.
- Prefer a cheap probe when two probes split the possibilities equally well.
- Do not change the system until evidence points to a cause.
Example
- The provider status page is easy but identical for every candidate cause. The network response body may split client, backend, provider, and database failures in one step.
Ask next
- ?Which candidates remain?
- ?How would this probe partition them?
- ?Am I gathering evidence or merely activity?