9.48 Acid gases must be removed from other refinery gases in chemical production facilities in order to minimize corrosion of the plants. Two methods for removing acid gases produced the corrosion rates

(in mm/yr) are listed below in experimental tests:

Method A: 0.3, 0.7, 0.5, 0.8, 0.9, 0.7, 0.8 Method B: 0.7, 0.8, 0.7, 0.6, 2.1, 0.6, 1.4, 2.3 Estimate the difference in mean corrosion rates for the two methods, using a confidence coefficient of 0.90. What assumptions must you make for your answer to be valid? (The data come from Kosseim et al., Chemical Engineering Progress, 80, 1984, p. 64.)