Reconsider the axial stiffness data given in Exercise 8. ANOVA output from Minitab follows:

Pooled StDev = 32.39.
Tukey's pair-wise comparisons
Family error rate = 0.0500
Individual error rate = 0.00693
Critical value = 4.10
Intervals for (column level mean) - (row level mean).

a. Is it plausible that the variances of the five axial stiffness index distributions are identical? Explain.
b. Use the output (without reference to our F table) to test the relevant hypotheses.
c. Use the Tukey intervals given in the output to determine which means differ, and construct the corresponding underscoring pattern?

Analysis of Variance for Stiffness Source Length Error Total DF 4 30 3 4 MS 10998 1049 43993 31475 75468 Mean 7 333.21 7 368.06 7 375.13 7 407.36 7 437.17 10.48 0.000 Level 4 6 StDev 36.59 28.57 20.83 44.51 26.00 10 12 2 40 28 28 21 81 11 8 31 59 39 73 90 98 54 81 11 6 04 13 39 28 55 28 43 43 8-9 4 22 55 6 1 8