7-22. Two different analytical methods were used to deter- mine residual chlorine in sewage effluents. Both meth- ods were used on the same samples, but each sample came from various locations with differing amounts of contact time with the effluent. Two methods were used to determine the concentration of Cl in mg/L, and the results are shown in the following table: Sample Method A Method B 0.39 0.84 1 0.36 1.35 2.56 2 3 1.76 4 3.35 3.92 4.69 5.35 6 7.70 8.33 7 10.52 10.70 8. 10.92 10.91 (a) What of t test should be used to compare the type two methods and why? (b) Do the two methods give different results? State and test the appropriate hypotheses. (c) Does the conclusion depend on whether the 90%, 95%, or 99% confidence levels are used?