In the article “Effect of irradiation on grip strength” published in the Journal of Korean Academy of University Trained Physical Therapists (Sang-hyub, 1999), the author reported the results of a two-factor experiment on grip strength. The two factors in the experiment were dominant hand (Yes, No) and irradiation (ball, no ball), and each of the four treatments was replicated 30 times. The response variable in this study was grip strength. Use the ANOV table given in Table 12.41, which was reported in this article, to answer the following:

(a) Estimate the standard deviation of the experimental error.

(b) On the basis of ????-ratios is there sufficient evidence to conclude that the factors interact?

(c) On the basis of their ????-values in Table 12.41, is there sufficient evidence to conclude that these two factors affect grip strength? Explain.

(d) On the basis of their ????-values in Table 12.41, which means should be separated?