Four chemical plants, producing the same product and owned by the same company, discharge effluents into streams in the vicinity of their locations. To check on the extent of the pollution created by the effluents and to determine whether this varies from plant to plant, the company collected random samples of liquid waste, five specimens for each of the four plants. The data are shown in the table:

a. Do the data provide sufficient evidence to indicate a difference in the mean amounts of effluents discharged by the four plants?
b. If the maximum mean discharge of effluents is 1.5 lb/gal, do the data provide sufficient evidence to indicate that the limit is exceeded at plant A?
c. Estimate the difference in the mean discharge of effluents between plants A and D, using a 95% confidence interval.

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Plant Polluting Effluents (lb/gal of waste) 1.65 1.72 50 37 1.60 B 1.70 1.85 462.05 1.80 1.40 1.75 1.38 165 .55 D 2.10 1.95 65 188 2.00