Statistical analysis proficiency testing

As shown above, these include a laboratory to be third-party assessed to international accreditation standards, to demonstrate that it is in statistical control by using appropriate internal quality control procedures, to participate in proficiency testing schemes which provide an objective means of assessing and documenting the reliability of the data it is producing and to use methods of analysis that are fit-for-purpose . These requirements are summarised below and then described in greater detail later in this chapter. 

Within two weeks of the study closing date, we issue an interim report, the purpose of which is to provide rapid feedback to participants. At the conclusion of each study, a detailed final report is prepared and issued to participants. This report contains a full description of the study together with statistical analysis and graphical presentation of the results. The report is prepared in a standardised format consistent with ISO and ILAC guidelines for proficiency test reports. 

The Technical Services function of AOCS establishes, revises, and annually updates AOCS Methods, the Official Methods and Recommenced Practices of the American Oil Chemists Society22 for fats, oils, and soap technology Spanish AOCS Methods, a Spanish translation of the more commonly used AOCS Methods and Physical and Chemical Characteristics of Oils, Fats and Waxes. Leaders of the methods development committees coordinate closely with AOAC International (formerly the Association of Official Analytical Chemists). AOCS Methods are recognized as Official Methods in US FDA activities and when litigation becomes necessary in industry trade. Additionally, the Technical Services function operates a Laboratory Proficiency Program (formerly the Smalley Check Sample Program) and oversees distribution and statistical analysis of 30 different series of basic laboratory quality assur-ance/quality control test samples. Certification as AOCS Approved Chemists, or as AOCS... 

New. A new microscale titration experiment is included, provided by Professor John Richardson from Shippensburg State University, for the analysis of hard-water samples (Experiment 18). The tools an4 techniques used for that experiment could be used to design similar experiments for other titrations if desired. (If your in-stractor tries this with you, I may include your experiment in the next edition ) Two team experiments are added (Experiments 39 and 40) to illustrate the principles presented in Chapter 4 on statistical validation. One is on method validation and quality control, in which different members of teams perform different parts of the validation for a chosen experiment. The other is on proficiency testing, in which you calculate the z-values for all the student results of one or more class experiments and you compare your z-value to see how well you have performed. 

In addition to references to specific literature sources, a bibliography is given at the end of the chapter for appropriate statistical textbooks and for ASTM and ISO standards that iipply to quality assurance, statistical analysis, precision, bias and uncertainty, laboratory accreditation, and proficiency testing. The listing of standards is not exhaustiv e only those that are anticipated to be worthwhile for the topic of this chapter are included. These standards, with some exceptions as noted, were developed by committees on statistics and quality as generic standards that apply in principle to all testing and measurement operations. 

Internal Control Limits. The laboratory protocol for evaluating internal QC analyses per control limits should be clearly defined. Limits may be based on statistical methods (e.g., as 2d from the laboratory mean recovery), or on proficiency testing limits (e.g., 1 pg or 15% of the mean, whichever is greater). Statistical limits that exceed 40% should be reevaluated to determine the source error in the analysis. 

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