Sample size calculator

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Result

Sample size139

Step-by-step solution

Solve E = z·σ/√n for n

n = (z·σ/E)² = (1.96·12/2)² = 138.3

round up: n = 139

Key formulas

Sample size: n = (z·σ/E)², rounded up
Critical z: 90%: 1.645, 95%: 1.96, 99%: 2.576

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