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?

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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