Analytical Chem istry - DePauw University

Chapter 4 Evaluating Analytical Data141in human serum samples was determined by the improved method andthe standard method. The results, with concentrations in mmol/L, areshown in the following table.Sample Improved Method Standard Method1 8.25 8.062 9.75 8.843 9.75 8.364 9.75 8.735 10.75 13.136 11.25 13.657 13.88 13.858 14.25 13.53Determine whether there is a significant difference between the twomethods at a = 0.05.30. Ten laboratories were asked to determine an analyte’s concentration ofin three standard test samples. Following are the results, in mg/mL. 29Laboratory Sample 1 Sample 2 Sample 31 22.6 13.6 16.02 23.0 14.2 15.93 21.5 13.9 16.94 21.9 13.9 16.95 21.3 13.5 16.76 22.1 13.5 17.47 23.1 13.9 17.58 21.7 13.5 16.89 22.2 12.9 17.210 21.7 13.8 16.7Determine if there are any potential outliers in Sample 1, Sample 2 orSample 3 at a significance level of a = 0.05. Use all three methods—Dixon’s Q-test, Grubb’s test, and Chauvenet’s criterion—and comparethe results to each other.Many of the problems that follow require accessto statistical tables. For your convenience,here are hyperlinks to the appendices containingthese tables.Appendix 3: Single-Sided Normal DistributionAppendix 4: Critical Values for the t-TestAppendix 5: Critical Values for the F-TestAppendix 6: Critical Values for Dixon’s Q-TestAppendix 7: Critical Values for Grubb’s Test31. When copper metal and powdered sulfur are placed in a crucible andignited, the product is a sulfide with an empirical formula of Cu x S. Thevalue of x can be determined by weighing the Cu and S before ignition,and finding the mass of Cu x S when the reaction is complete (any excesssulfur leaves as SO 2 ). The following table shows the Cu/S ratios from62 such experiments.29 Data adapted from Steiner, E. H. “Planning and Analysis of Results of Collaborative Tests,” inStatistical Manual of the Association of Official Analytical Chemists, Association of Official AnalyticalChemists: Washington, D. C., 1975.