Checklist
Use an independent check only when it is truly independent
Two signatures can still be one mistake copied twice.
When it fits
- A high-risk result receives a second check but both reviewers may share the same source, calculation or assumption.
When to avoid it
- Full independence is expensive and sometimes impossible; document shared dependencies instead of overstating redundancy.
Checklist
- The checker can reconstruct the critical result independently.
- The original answer is hidden initially when feasible.
- Different source data or calculation path is used where appropriate.
- Disagreement must be resolved rather than averaged silently.
- The check is reserved for risks that justify the extra cost.
Why it matters
For catastrophic or irreversible decisions, design the second check to add different evidence or recomputation rather than merely rereading the same output. Hide the first result initially when anchoring matters. Compare discrepancies explicitly before approval.
An example
A second person independently recomputes the affected record count from source keys before a mass deletion.
Check your result
The second check could realistically catch an error made by the first path.
Keep this limit in mind
- Full independence is expensive and sometimes impossible; document shared dependencies instead of overstating redundancy.
Evidence and sources
Supports
Redundancy and independent checks can increase reliability when a single failure would have unacceptable consequences.
Redundancy can fail jointly when checks share the same information, assumptions or interface.
Staff Empowerment: System design, behavioral choices, learning systems and accountability · Forcing functions, checks and redundancies