Margin of Error
Half-width for mean estimate at chosen confidence.
Inputs
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Formula
MoE = z* × (σ/√n)
Margin of error is the plus-minus band around the sample mean for interval estimation.
Worked example
σ=10, n=100 at 95% gives MoE ≈ ±1.96.
Where this can give the wrong answer
- Same z-table limits as CI calculator.
- Polls often report MoE for proportions — different formula.
- Non-response bias not captured.
FAQ
- Quadruple n — MoE scales as 1/√n.