CHAPTER 3

3. For a lower confidence level, the confidence interval will be smaller (narrower) since only a 90 percent degree of confidence is required. For a 90 percent confidence level with 10 degrees of freedom, the t-value is 1.812. Confidence interval = Predicted cost ± (t-value × Standard error) = $19,209 ± (1.812 × $513.68) = $19,209 ± $931 ................
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