VetsLearn — Analyze data & support decisions — 01: Define the question and the data contract
Revision 2026-10-03; fictional training fixture.

OUTCOME
Specify the unit of analysis before calculating.

INDEPENDENT TASK
Independent rows: X closed 20 minutes; Y closed 40; Z open blank; W closed duration -5. Define a contract and an analysis plan before calculating.

STEPS
1. State the population, row meaning and unit.
2. Flag W as invalid and Z as open, rather than silently deleting them.
3. Calculate a valid observed closed-request mean and report exclusions.

ACCEPTANCE CRITERIA
- Mean of valid observed closed durations is 30 minutes.
- Report one open and one invalid record.
- Do not claim a mean for all requests or treat blanks as zero.

EXPLAIN YOUR APPROACH
What additional data would you need for a complete closed-request average?

Keep your artifact, corrections, evidence and limitations yourself.
Self-review is not independent assessment. No paid model calls are required.
Review notes: /paths/analysis/01/#practice