A defined observation or pattern that prompts investigation because the current process may no longer match its baseline, without by itself proving a cause or prescribing a response.

# Diagnostic signal

This is an editorial synthesis. A signal becomes actionable only when its measure, baseline, rule and investigation owner are declared. A threshold copied from another process is not automatically meaningful.

## Sources

- nist-process-control-signals (primary)
- nist-correlation-causality (primary)