Quality assurance uncertainty

For example, if ever we want to understand whether global warming to a substantial degree is, or is not, caused by human activities, then we should first of all know and understand the performance of our models and the accuracy of data we put into these models. If ever we want to know whether all efforts to improve the quality of the sea for biota are effective, then we need to know the accuracy and uncertainty of all our data. If we do not want to take Quality Assurance into account, we will never be able to lay the solid scientific foundations for our research, political and legal actions etc. In other words we will remain only believers. 

The principles of quality assurance are commonly related to product and process control in manufacturing. Today the field of application greatly expanded to include environmental protection and quality control within analytical chemistry itself, i.e., the quality assurance of analytical measurements. In any field, features of quality cannot be reproduced with any absolute degree of precision but only within certain limits of tolerance. These depend on the uncertainties of both the process under control and the test procedure and additionally from the expense of testing and controlling that may be economically justifiable. 

However, since the data used in this study are subject to the limitations and uncertainties cited above, the results of this analysis represent only a very rough approximation of the national frequency distribution of indoor radon levels. EPA s national survey will seek to more accurately characterize this distribution through use of a larger sample size, a statistically based survey design, and consistent, quality assured sample collection and measurement procedures. 

This chapter deals with handling the data generated by analytical methods. The first section describes the key statistical parameters used to summarize and describe data sets. These parameters are important, as they are essential for many of the quality assurance activities described in this book. It is impossible to carry out effective method validation, evaluate measurement uncertainty, construct and interpret control charts or evaluate the data from proficiency testing schemes without some knowledge of basic statistics. This chapter also describes the use of control charts in monitoring the performance of measurements over a period of time. Finally, the concept of measurement uncertainty is introduced. The importance of evaluating uncertainty is explained and a systematic approach to evaluating uncertainty is described. 

This chapter has considered two key aspects related to quality assurance - the use of control charts and the evaluation of measurement uncertainty. These activities, along with method validation, require some knowledge of basic statistics. The chapter therefore started with an introduction to the most important statistical terms. 

Measurement uncertainty is one of the key issues in quality assurance. It became increasingly important for analytical chemistry laboratories with the accreditation to ISO/IEC 17025. 

Measurement uncertainty is the key to understanding modern approaches to quality assurance in analytical chemistry. A proper measurement uncertainty gives a range in which the value of the measurand is considered to... 

There are some existing texts that cover the material in this book, but I have tried to take a holistic view of quality assurance at a level that interested and competent laboratory scientists might learn from. I am continually surprised that methods to achieve quality, whether they consist of calculating a measurement uncertainty, documenting metrological traceability, or the proper use of a certified reference material, are still the subject of intense academic debate. As such, this book runs the risk of being quickly out of date. To avoid this, I have flagged areas that are in a state of flux, and I believe the principles behind the material presented in this book will stand the test of time. 

Field intercomparisons are another important quality assurance step for quantifying the uncertainty of methods they also include the sampling uncertainty and not just the analytical uncertainty... 

The uncertainty analysis should be subject to an evaluation process that may include peer review, model comparison, quality assurance or comparison with relevant data or independent observations. 

This chapter aims to provide a step-by-step guide for practitioners involved in the collection of contaminated samples by reviewing current groundwater sampling techniques and procedures and highlighting the major sources of uncertainty associated with sample collection. On-site water-quality measurements, quality assurance procedures and sample handling techniques designed to maintain the representativeness of the sample from field to laboratory are also discussed. 

L. Jorhem, J. Engman, B. Sundstrom, A. Nilsson, Evaluation of measurement data for Cd, Cr and Pb in certain uncontaminated foodstuffs published in surveys analytical quality vs. uncertainty of measurements, J. Accred. Qual. Assur., 10 (2006), 647-658. 

Renn O, Benighaus C. 2006. Framing the perception of cumulative stressors, especially chemical risks. Report on approaches to the characterization of knowledge of risks, uncertainties and ambiguity and their use and quality assurance in the IP domain. EU FP6 Project NOMIRACLE, Deliverable 4.3.2. Stuttgart (DE) Dialogik. 

Quality assurance and quality control (QA/QC) A system of procedures, checks, and audits to judge and control the quality of measurements and reduce the uncertainty of data. Some quality control procedures include having more than one person review the findings and analyzing a sample at different times or using different laboratories to see if the findings are similar Quantitative risk assessment (QRA) A process that relies on mathematical modeling and estimations usually derived from animal test results and the probability of risk for a chemical substance at the low dose to which the human population is normally exposed Radionuclide A nuclide with radioactive properties... 

The analysis of nitric-perchloric acid digests of feed samples for a local industry presented an early test of the ICAP analysis of organic samples. The results obtained for Association of American Feed Control OflBcials (AAFCO) feed check samples (included as quality assurance standards within the sample suite) are given in Tables V and VI. The ICAP results for iron, copper, zinc, manganese, cobalt, and potassium are all within the uncertainty limits of the certified values. While not within the uncertainty limits, the results for calcium, magnesium, sodium, and phosphorus compare with acceptable agreement for the intended application. 

In many countries undertaking the most technically demanding analyses, it is expected that the laboratories will be registered under quality assurance schemes. Accuracy and repeatability should be covered by quality assurance requirements, but resolution and detection limits are critically dependent on technique and instrumentation. Details on the general subjects of quality assurance/quality control, quantification of uncertainty in analytical measurements, accreditation of laboratories, and on the general concepts and strategy for ensuring that analytical chemical measurements are comparable - in one word traceability - can be found elsewhere in the chemical literature (26,32-36). 

ISO 8402 (1994) Quality management and quality assurance - vocabulary. BIPM/IEC/IFCC/ISO/IUPAC/IUPAP/ OIML (1995) Guide to the expression of uncertainty in measurement. 

Keywords Accuracy Analytical procedure Measurement assurance Measurement uncertainty Quality assurance Validation... 

This article deals with legal requirements in the European Union on basic principles of laboratory quality assurance for official notification to the EC Commission and on method validation concerning official laboratories. Widespread discussions and activities on measurement uncertainty are in progress, and the European validation standards for official purposes may serve as a basis for world-wide efforts on quality harmonization of analytical results. Although much time has already been spent, definitions and require-... 

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