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A sample of 21 minivan electrical warranty repairs for loose

A sample of 21 minivan electrical warranty repairs for "loose, not attached" wires (one of several electrical failure categories the dealership mechanic can select) showed a mean repair cost of $45.66 with a standard deviation of $27.79.

(a) Construct a 95 percent confidence interval for the true mean repair cost.

(b) How could the confidence interval be made narrower? (Data are from a project by MBA student Tim Polulak.)

(a) Construct a 95 percent confidence interval for the true mean repair cost.

(b) How could the confidence interval be made narrower? (Data are from a project by MBA student Tim Polulak.)

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