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The margin of error (MOE) quantifies the uncertainty in a survey result. A poll showing 60% support with ±4% MOE means the true population value likely falls between 56–64% at the stated confidence level. MOE shrinks as sample size grows.
Przewodnik krok po kroku
- 1MOE = z × √(p(1-p)/n)
- 2z = 1.96 for 95% confidence
- 3p = observed proportion · n = sample size
- 4MOE is the ± value reported alongside poll results
Rozwiązane przykłady
Wejście
n=1,000 · p=0.5 · 95% confidence
Wynik
MOE = ±3.1%
1.96×√(0.25/1000)=0.031
Wejście
n=400 · p=0.5 · 95% confidence
Wynik
MOE = ±4.9%
Halving n roughly doubles the MOE
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