# Build the 80% confidence interval for a mean using t distribution

We are evaluating the sheet metal scrap rate in a contractor proposal. Based on a sample of 28 parts you calculate a mean rate of 6.50% (treat as 6.50) and a standard deviation of 1.20. Calculate a 80% confidence interval to be used to support negotiations. (Carry intermediate calculations to three decimal places.)

6.18 ≤ μ ≤ 6.82

6.20 ≤ μ ≤ 6.80

6.08 ≤ μ ≤ 6.92

6.43 ≤ μ ≤ 6.57

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We are given the following values: n=28, significance level=80%, mean=6.5 and ...

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The solution gives detailed steps on building the 80% confidence interval for a mean using t distribution.

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