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CSSBB Six Sigma Black BeltQuestion 4 / 10

Henderson determines that a sample size of 138 is required to determine, with 95% confidence (α = 0.05), the maximum proportion of defective 50 mm copper piping in the population. What is the calculated proportion (p̂)?

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✓ Correct answer: B. 0.10 To calculate the proportion (p̂), we can use the equation n = (Zα/2/E)2 p̂(1 - p̂), where: α = 0.05 E = 0.05 p̂ = ? n = 138 Referring to a standard normal distribution table, we find that α/2 (0.025) corresponds to Z = 1.96. Plugging in the values, we can solve for p̂: 138 = ((1.96)/0.05))2 (p̂(1-p̂)). After solving the equation, we find that p̂ = 0.10

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