CF Dictionary · Decision Making
Margin of Error
The imprecision around a measurement or breakpoint. CF uses it to handle borderline cases and to design buffer.
Also: tolerance, robustness, resilience
A margin of error (also: tolerance, robustness, resilience) is the imprecision around a measurement or around a breakpoint. If the breakpoint is at $20 and the margin is ±$2, then values from $18 to $22 are borderline.
Margins matter
- Breakpoints aren't infinitely sharp. Real measurements have noise.
- You need to handle borderline cases. Round, re-measure, or proceed with caution.
- Design margin into systems. Buffers are deliberate margin.
What CF says about margins
- If margin > category size, your categories are too small; fix the breakpoints or measure more precisely.
- If margin < factor size, your measurement is fine.
- Aim for margin < difference between options. Otherwise you can't tell them apart.
Margin in design
- Engineering tolerances. "This screw must be 5mm ± 0.1mm."
- Quality assurance. "This dimension has a 0.5% tolerance."
- Risk management. "We have a 10% error bar on the estimate."
CF's recommendation
- Don't optimise inside your margin. You'll just be moving noise around.
- Do design margin for resilience. Real systems vary.
- Do buffer your bottlenecks. Protect them from variance.
"Pass/fail grades: Binary evaluation approach for factors with excess capacity." — LessWrong summary of CF