The AGENTS data set contains the results of an experiment using polymers to clean coal. The cleansing efficiencies of three polymers ('I', 'II', and 'III') are compared. To assess the efficiency of the cleansing operation, the amount of suspended solids in the overflow solution is measured in milligrams per liter. The more efficient operation produces more suspended solids in the overflow. Six data points are collected on each of the three polymers. In addition, the pH of the cleansing tank is measured each time in case pH affects the cleansing efficiency.
One-way analysis of variance (with variable SOLIDS as the response variable and variable POLYMER as the classification variable) can be used to compare the cleansing efficiency of the three polymers. Variable PH can be used as a covariate in analysis of covariance.