15.69 Pollution from Chemical Plants In Exercise 11.64, you performed an analysis of variance to compare the mean levels of effluents in water at four different industrial plants (see data set EX1164). Five samples of liquid waste were taken at the output of each of four industrial plants. The data are shown in the table: 

a. Do the data present sufficient evidence to indicate a difference in the levels of pollutants for the four different industrial plants? Test using the appropriate nonparametric test.

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

c. Compare the test results in part a with the analysis of variance test in Exercise 11.64. Do the results agree? Explain.

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Plant Polluting Effluents (400 g/4 L of waste) ABCD 1.65 1.72 1.50 1.37 1.60 1.70 1.85 1.46 2.05 1.80 1.40 1.75 1.38 1.65 1.55 2.10 1.95 1.65 1.88 2.00