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A sample of 36 sheets of metal from a large normal population has a mean thickness...

A sample of 36 sheets of metal from a large normal population has a mean thickness of 30 mm. We know from previous quality control testing that the population standard deviation is 3.3 mm. Develop a 95% confidence interval for the true mean for the population.

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Answer #1

95% confidence interval for is

- Z * / sqrt(n) < < + Z * / sqrt(n)

30 - 1.96 * 3.3 / sqrt(36) < < 30 + 1.96 * 3.3 / sqrt(36)

28.922 < < 31.078

95% CI is ( 28.922 , 31.078 )

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