A civil engineer is analyzing the compressive strength of concrete. Compressive strength is normally distributed with o? = 1000 (psi)?. A random sample of 12 specimens has a mean compressive strength of X = 3250 psi. 1. *Construct a 95% two-sided confidence interval on mean compressive strength. 2. *Construct a 99% two-sided confidence interval on mean compressive strength. Compare the width of this confidence interval with the width of the one found in part (1).

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