9. Toxic Chemicals To compare the effects of three toxic chemicals, A, B, and C, on the skin of rats, 2-centimeter-side squares of skin were treated with the chemicals and then scored from 0 to 10 depending on the degree of irritation. Three adjacent 2-centimeter-side squares were marked on the backs of eight rats, and each of the three chemicals was applied to each rat. Thus, the experiment was blocked on rats to eliminate the variation in skin sensitivity from rat to rat.

a. Do the data provide sufficient evidence to indicate a difference in the toxic effects of the three chemicals?
Test using the Friedman F -test r with a 5.05.

b. Find the approximate p-value for the test and interpret it.

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Rat 1 2 3 4 5 6 7 00 8 B 5 AA A 9 96 C B 6 8 96 C 4 69 B B 8 8 CSAS C B 5 5 7 5 BC B A 7 6 C 3 68 B 9 Um C 3 5 AT AS 7 B7 AG C 6 7