A civil engineer is analyzing the compressive strength of concrete. Compressive strength is normally distributed with 62 = 1000 psi. A random sample of 12 sample specimens has a mean compressive strength of x = 3204 psi. Round your answers to 1 decimal place. (a) Calculate the 95% two-sided confidence interval on the true mean compressive strength of concrete. i SHE i (b) Calculate the 99% two-sided confidence interval on the true mean compressive strength of concrete. SHE