Question 597168
He controls his manufacturing process so that the proportion of faulty products is supposed to be only 5%. Out of 400 supplies in a batch, 26 prove to be faulty. Verify the manufacturer’s claim. Use 0.05 level of significance. 
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Ho: p = 0.05 (claim)
Ha: p # 0.05
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Sample proportion: 26/400 = 0.065
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Test statistic: z(0.065) = (0.065-0.05)/sqrt[0.05*0.95/400] = 1.3765
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p-value = 2*P(z > 1.3765) = 2*0.08 = 0.16
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Conclusion: Since the p-value is greater than 5%, 
fail to reject Ho. The test results support the claim.
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Cheers,
Stan H.