Compressive strength of concrete is affected by several factors, including composition (sand, cement, etc.), mixer type (batch vs. continuous), and curing procedure. Accordingly, a concrete company is conducting an experiment to determine how mixing technique affects the resulting compressive strength. Four potential mixing techniques have been identified. Subsequently, samples of 20 specimens have been subjected to each mixing technique, and the resulting compressive strengths (in pounds per square inch, psi) were measured. A portion of the data is shown in the accompanying table.

Mix Tech. 1 (psi) Mix Tech. 2 (psi)Mix Tech. 3 (psi)Mix Tech. 4 (psi)

2972...........................2794.....................2732.......................2977

2818...........................3162.....................2905.......................2986

⋮...................................⋮...........................⋮..............................⋮

2665...........................2837.....................3073.......................3081

a. Construct an ANOVA table. Assume compressive strengths are normally distributed.

b. Specify the competing hypotheses to test whether there are some differences in the mean compressive strengths across the four mixing techniques.

c. At the 5% significance level, what is the conclusion of the test? What about the 1% significance level?