(b) An accredited laboratory participated in a proficiency program. The following table shows the test results of the laboratory as well as the assigned values and their standard deviations from the PT organizer. Results from Values from PT Organizer (mg/kg) Metals the Lab Assigned Standard (mg/kg) value deviation As 4.27 8.34 0.97 cd 0.57 0.39 0.07 Fe 6.8 6.0 0.7 Mn 0.74 0.76 0.12 Zn 73.0 68.4 5.8 Calculate the rescaled sum of z-scores (RSZ) as well as the sum of squared Z-scores (SSZ) for the overall performance of the laboratory on those metals. Are the two scores are satisfactory or not? Comment on the advantages or disadvantages of using these two scores. (Given: For Chi-square distribution, at degree of freedom=4 with 99% confidence interval, the calculated value greater than 13.28 is considered to be unsatisfactory.) (12 marks) 1 A cold vapour atomic absorption method was employed for the determination of mercury content in fishery products. During the method validation, a certified reference material DORM-2, which is a dogfish muscle, was analyzed six times and the results are shown on the following table. Certified value of mercury content in DORM-2 Observed values Expanded Standard Concentration uncertainty with Mean deviation k=2 (mg/kg) (mg/kg) (mg/kg) (mg/kg) 4.35 0.22 3.92 0.17 (a) Calculate the recovery Rm as well as the standard uncertainty of the recovery (R.). (b) Test whether the observed recovery is significantly different from one by using Ieri 2. (c) If the observed recovery is found to be significantly different from one, suggest two ways to deal with this