An engineer wants to know if the mean strengths of three different concrete mix designs differ significantly. He randomly selects nine cylinders that measure 6 inches in diameter and 12 inches in height in which mixture 67-0-301 is poured, nine cylinders of mixture 67-0-400, and nine cylinders of mixture 67-0-353. After 28 days, he measures the strength (in pounds per square inch) of the cylinders. The results are presented in the following table:

(a) State the null and alternative hypotheses.
(b) Explain why we cannot use one-way ANOVA to test these hypotheses.