A manufacturer of air conditioning ducts is concerned about the variability of the tensile strength of the sheet metal among the many suppliers of this material. Four samples of sheet metal from four randomly chosen suppliers are tested for tensile strength. The data are given in Table 6.26.

(a) Perform the appropriate analysis to ascertain whether there is excessive variation among suppliers.

(b) Estimate the appropriate variance components.

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Table 6.26 Data for Exercise 9. Supplier 1 2 3 4 19 80 47 21 71 48 90 26 49 49 Supplier 1 2 3 4 19 29 22 58 63 25 83 56 35 78