TY - JOUR A1 - Wilrich, Cordula A1 - Wilrich, Peter-Th. T1 - Method for the design and evaluation of binary sensitivity tests N2 - For many materials or specimen, their resistance to stress is an important (safety) characteristic. The target value is the event stress, i.e. the value of the stress at which the (adverse) event occurs. Depending on the test procedure and the test items, the event stress cannot always be measured directly but must be determined by binary sensitivity tests. A method for the evaluation of binary sensitivity tests based on the principle of Maximum Likelihood is presented and compared to other methods (traditionally) applied. Sensitivity testing of explosives and fatigue testing of metallic materials are used as real examples to illustrate application of the method and to compare actual results. The method presented delivers not only the estimate of the stress at any specified probability of the event but also the respective 95 % confidence interval. Application of the method is facilitated because it does not require the data to be obtained in a staircase procedure, can process any kind of input data (e.g. as measured or logarithmic), and does not require the stress levels to be equidistant. The method is easily applicable for any laboratory because it is implemented into an Excel file, which is made freely available at https://www.statistics-wilrich.info. KW - BAM Fallhammer KW - Fatigue limit KW - Impact sensitivity KW - Safety characteristic KW - Staircase procedure KW - Up-and-down procedure PY - 2024 DO - https://doi.org/10.1515/mt-2024-0176 VL - 66 IS - 11 SP - 1931 EP - 1944 PB - Walter de Gruyter GmbH CY - Berlin AN - OPUS4-61418 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wilrich, Cordula A1 - Wilrich, Peter-Th. T1 - Estimation of the POD function and the LOD of a qualitative microbiological measurement method N2 - Qualitative microbiological measurement methods in which the measurement results are either 0 (microorganism not detected) or 1 (microorganism detected) are discussed. The performance of such a measurement method is described by its probability of detection as a function of the contamination (CFU/g or CFU/mL) of the test material, or by the LODp, i.e., the contamination that is detected (measurement result 1) with a specified probability p. A complementary log-log model was used to statistically estimate these performance characteristics. An intralaboratory experiment for the detection of Listeria monocytogenes in various food matrixes illustrates the method. The estimate of LOD50% is compared with the Spearman-Kaerber method. KW - POD KW - LOD KW - Statistical method KW - Qualitative measurement PY - 2009 DO - https://doi.org/10.1093/jaoac/92.6.1763 SN - 1060-3271 VL - 92 IS - 6 SP - 1763 EP - 1772 PB - AOAC International CY - Arlington, Va. AN - OPUS4-20755 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jarvis, B. A1 - Wilrich, Cordula A1 - Wilrich, Peter-Th. T1 - Reconsideration of the derivation of most probable numbers, their standard deviations, confidence bounds and rarity values N2 - Aims: The purpose of this work was to derive a simple Excel spreadsheet and a set of standard tables of most probable number (MPN) values that can be applied by users of International Standard Methods to obtain the same output values for MPN, SD of the MPN, 95% confidence limits and test validity. With respect to the latter, it is considered that the Blodgett concept of 'rarity' is more valuable than the frequently used approach of improbability (vide de Man). Methods and Results: The paper describes the statistical procedures used in the work and the reasons for introducing a new set of conceptual and practical approaches to the determination of MPNs and their parameters. Examples of MPNs derived using these procedures are provided. The Excel spreadsheet can be downloaded from http://www.wiwiss.fu-berlin.de/institute/iso/mitarbeiter/wilrich/index.html. Conclusions: The application of the revised approach to the determination of MPN parameters permits those who wish to use tabulated values, and those who require access to a simple spreadsheet to determine values for nonstandard test protocols, to obtain the same output values for any specific set of multiple test results. The concept of 'rarity' is a more easily understood parameter to describe test result combinations that are not statistically valid. Provision of the SD of the log MPN value permits derivation of uncertainty parameters that have not previously been possible. Significance and Impact of the Study: A consistent approach for the derivation of MPNs and their parameters is essential for coherence between International Standard Methods. It is intended that future microbiology standard methods will be based on the procedures described in this paper. KW - Confidence bounds KW - Microbiological analyses KW - Most probable number KW - MPN KW - Rarity value PY - 2010 DO - https://doi.org/10.1111/j.1365-2672.2010.04792.x SN - 1364-5072 VL - 109 IS - 5 SP - 1660 EP - 1667 PB - Wiley-Blackwell CY - Malden, Mass., USA AN - OPUS4-22168 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jarvis, B. A1 - Wilrich, Cordula A1 - Wilrich, Peter-Th. T1 - Estimation of the POD function and the LOD of a binary microbiological measurement method from an interlaboratory experiment N2 - Background: We deal with interlaboratory experiments (collaborative studies) in which k participating laboratories, selected randomly from a population of laboratories, use samples from one and the same material or matrix. They perform binary microbiological measurements for which the measurement results are either “0” (target microorganisms not detected) or “1” (target microorganisms detected). The performance of such a measurement method is described by its probability of detection (POD) function, i.e., the POD as a function of the contamination of the sample (CFU per gram or CFU per milliliter), or by the level of detection (LODp), i.e., the contamination level of the sample that is detected (measurement result “1”) with a specified probability p. Objective: We derive an approximate statistical analysis that is simple enough to be implemented in a spreadsheet application. Methods: Under the assumption of a Poisson distribution of the number of CFU in the samples, we estimate the mean POD function of the laboratories and the SD of the laboratory effect based on a complementary log-log model, a special case of the Generalized Linear Model in the special situation in which the contamination level is known by means other than the POD. The estimates are obtained by maximization of the Laplace approximation of the likelihood function. By simulation, a bias correction factor for the estimate of the SD is obtained. With the estimated POD function, LODs can be estimated. The model can also be used to evaluate the relative LOD of an alternative method with repect to a reference method. Results: The EXCEL program PODLOD-interlab_ver1.xls for this method of statistical analysis can be downloaded from http://www.wiwiss.fu-berlin.de/fachbereich/vwl/iso/ehemalige/wilrich. Highlights: A simple approximate statistical method for the estimation of the POD and LOD is derived. The method also allows the estimation of the RLOD of an alternative Microbiological Methods Received December 11, 2018. Accepted by AH April 5, 2019. Estimation of the POD Function and the LOD of a Binary Microbiological Measurement Method from an Interlaboratory Experiment Basil Jarvis, Ross Biosciences Ltd, Upton Bishop, Ross-on-Wye HR9 7UR, United Kingdom; Cordula Wilrich, Bundesanstalt für Materialforschung und –prüfung, Unter den Eichen 87, D-12205 Berlin, Germany; Peter-Theodor Wilrich, Freie Universität Berlin, Institut für Statistik und Ökonometrie, Garystrasse 21, D-14195 Berlin, Germany. DOI: https://doi.org/10.5740/jaoacint.18-0412 method with respect to reference method. The method is implemented in an EXCEL program that can be downloaded from http://www.wiwiss.fu-berlin.de/fachbereich/vwl/iso/ehemalige/wilrich. KW - Probability of detection KW - POD KW - Level of detection KW - Limit of detection KW - LOD KW - Interlaboratory experiment KW - Collaborative studies KW - Qualitative measurements KW - Binary measurement KW - Microbiological measurement PY - 2019 UR - https://aoac.publisher.ingentaconnect.com/contentone/aoac/jaoac/2019/00000102/00000005/art00042 DO - https://doi.org/10.5740/jaoacint.18-0412 SN - 1060-3271 SN - 1944-7922 VL - 102 IS - 5 SP - 1617 EP - 1623 PB - AOAC International CY - Gaithersburg, USA, MD, 20877-2504 AN - OPUS4-48883 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Müller, Christina A1 - Elagin, Mstislav A1 - Gaal, Mate A1 - Rosenthal, Martina A1 - Ewert, Uwe A1 - Osterloh, Kurt A1 - Wilrich, Peter-Th. T1 - Determination of reliability in demining and NDT N2 - The detection of defects in aircraft components or parts of a power plant or mines in the ground is connected with the task to distinguish between signals caused be the item searched for and noisy signals from other sources. The reliability of the system is the better the better the system is in detecting the wanted signal and avoiding false alarms caused by noise. It is usual to measure the reliability of diagnostic systems in terms of ROC-curves (Re-ceiver Operating Characteristics) and POD-curves (Probability of Detec-tion). The ROC curves describe the POD versus Probability of False Alarm with growing system sensitivity along the curve. POD curves describe the Probability of Detection for a fixed sensitivity for a variation of item sizes or depths. Reliability of the whole system is always a composition of the physics and technique, application influences and the human factors. For the scien-tific understanding and possibilities of improvement, decomposition accord-ing to a modular model is helpful. The authors present their experiences with the reliability evaluation of metal detectors for humanitarian demining and an NDT system of mechanized ultrasonic phased array testing of copper welds. The special concern in demining is the influence of soil types, detec-tors and the experiences of human beings. T2 - MATEST 2004 CY - Zagreb, Croatia DA - 2004-10-14 KW - Flaw Detection KW - Mine Detection KW - Prohability of Detection KW - Receiver Operating Characteristics KW - Metal Detector Test Trials PY - 2004 SN - 953-96225-9-X N1 - Geburtsname von Rosenthal, Martina: Scharmach, M. - Birth name of Rosenthal, Martina: Scharmach, M. SP - 183 EP - 201 AN - OPUS4-6047 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Gaal, Mate A1 - Müller, Christina A1 - Rosenthal, Martina A1 - Ewert, Uwe A1 - Lewis, A. A1 - Bloodworth, T. A1 - Wilrich, Peter-Th. A1 - Guelle, D. T1 - ITEP project 2.1.1.2 - Final report - Reliability model for test and evaluation of metal detectors N2 - Metal detectors used in demining have been tested within the frame of the International Test and Evaluation Programme project ITEP 2.1.1.2. Detection reliability tests were performed in accordance with the CEN workshop agreement describing specifications for test and evaluation (CWA 14747:2003). Results of these tests are aimed to verify and should help to optimise the proposed testing procedures. KW - Zuverlässigkeit der Minensuche KW - Feldtests KW - Modulares Modell KW - Metalldetektor PY - 2004 UR - http://www.itep.ws/pdf/Itep_no2.1.1.2_reliability_model.pdf N1 - Geburtsname von Rosenthal, Martina: Scharmach, M. - Birth name of Rosenthal, Martina: Scharmach, M. SP - 1 EP - 51 PB - Bundesanstalt für Materialforschung und -prüfung CY - Berlin AN - OPUS4-6049 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Christina A1 - Gaal, Mate A1 - Rosenthal, Martina A1 - Bär, Sylke A1 - Lewis, A. A1 - Bloodworth, T. A1 - Guelle, D. A1 - Wilrich, Peter-Th. T1 - ITEP-Test Trials for Detection Reliability Assessment of Metal Detectors N2 - The total reliability of a mine searching system is driven by the triple of intrinsic capability, which describes the physical-technical basis capability, the application and environmental factors and the human factors. Some of them can be determined in laboratory measurements but the human factor and a part of environment conditions and their interaction with the device need to be treated statistically. That is why the test & evaluation procedure described in CEN CWA 14747:2003, includes in addition to parameter tests of metal detectors also the reliability or blind field tests under local conditions with local personnel. A series of three big field trials had been accomplished in the ITEP-project 2.1.1.2 “Reliability Model for Test & Evaluation of Metal Detectors” to specify the optimum conditions for reliable trial results with affordable effort. For each set of specific working conditions, characterized in terms of a combination of one mine type in one soil with one detector handled by local personnel, the searching system will show up a working performance in mine detection rates as a function of mine depth and show up a certain overall false call rate. During the ITEP-trials in Benkovac and Oberjettenberg the authors learnt to determine this function separately for each mine type in each soil, which is especially important for low metal mines in uncooperative soil which will be illustrated for the mine PMA2 in different types of soil. The question of representativeness for field conditions on the one hand and necessary statistical set up for the possibility to distinguish between individual detector performances is still under discussion. KW - Zuverlässigkeit der Minensuche KW - Feldtests KW - Modulares Modell KW - Metalldetektor PY - 2005 UR - http://maic.jmu.edu/journal/8.2/rd/mueller.htm SN - 1533-9440 SN - 1533-6905 N1 - Geburtsname von Rosenthal, Martina: Scharmach, M. - Birth name of Rosenthal, Martina: Scharmach, M. IS - 8.2 SP - 86 EP - 90 CY - Harrisonburg AN - OPUS4-6041 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gaal, Mate A1 - Müller, Christina A1 - Ewert, Uwe A1 - Wilrich, Peter-Th. A1 - Spyra, W. T1 - Trial Design for Testing and Evaluation of Metal Detectors Used in Humanitarian Landmine Clearance T2 - 9th European Conference on NDT CY - Berlin, Germany DA - 2006-09-25 KW - Zuverlässigkeit in der Minensuche KW - Feldtests KW - Modulares Modell KW - Metalldetektor PY - 2006 SN - 3-931381-86-2 SP - 1(?) EP - 10(?) PB - European Federation for Non-Destructive Testing CY - Berlin AN - OPUS4-14420 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Müller, Christina A1 - Elagin, Mstislav A1 - Rosenthal, Martina A1 - Redmer, Bernhard A1 - Ewert, Uwe A1 - Schafer, Lloyd A1 - Wilrich, Peter-Th. T1 - Reliability Investigation of NDE Systems by Modular Analysis of Recorded Data N2 - During the second European-American Workshop on NDE Reliability, September 99 in Boulder, the term NDE reliability was defined as the degree that an NDT system is capable of achieving its purpose regarding detection, characterization and false calls. The most common – but also most expensive - way to determine this degree of capability in e.g. defect detection is to make just a performance demonstration using realistic test samples and to count the correct detections and false calls. For a more efficient way of reliability evaluation we propose to decompose the system into main modules e.g. according to the reliability formula set up on the first workshop: into f(IC) – a function of IC the intrinsic capability, determined by the physics and the technique of the NDE method representing an ideal upper bound of the reliability and g(AP) – a function of AP the industrial application factor like surface state or limited access to a component in general diminishing the ideal capability and finally h(HF) the function of the human factor which is in general also diminishing the ideal capability. The workshop proposed a rather plain mathematical shape for the formula R = f(IC) – g(AP) – h(HF) which should be considered merely as a “philosophical” expression but not as exact mathematical formula to be applied for evaluation of e.g. POD data. We propose to decompose the NDE system into modules in terms of functions of IC, AP and HF if appropriate or additional ones if necessary and then to analyze the mutual relationships of the terms via fault tree analysis. Finally the total reliability of the system is composed of the reliability of the subsystems via the rules of statistical systems theory. First trials for this approach of data analysis will be presented via examples from NDE systems in the aerospace industry. T2 - 8th ECNDT CY - Barcelona, Spain DA - 2002-06-17 PY - 2002 UR - http://www.ndt.net/article/ecndt02/428/428.htm N1 - Geburtsname von Rosenthal, Martina: Scharmach, M. - Birth name of Rosenthal, Martina: Scharmach, M. VL - 8 SP - 1(?) EP - 14(?) PB - European Federation for Non-Destructive Testing CY - Barcelona AN - OPUS4-2013 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Müller, Christina A1 - Rosenthal, Martina A1 - Wilrich, Peter-Th. A1 - Konchina, V. A1 - Markucic, D. A1 - Piscenec, Z. T1 - Proposals for Performance Demonstration and Modular Validation T2 - NDRF Summer Conference 2002 CY - Rosersberg, Sweden DA - 2002-08-28 PY - 2002 N1 - Geburtsname von Rosenthal, Martina: Scharmach, M. - Birth name of Rosenthal, Martina: Scharmach, M. SP - 1(?) EP - 10(?) AN - OPUS4-2017 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Müller, Christina A1 - Ewert, Uwe A1 - Rosenthal, Martina A1 - Völker, J. A1 - Schafer, Lloyd A1 - Wilrich, Peter-Th. T1 - Concepts in reliability measurement T2 - European-American Workshop 2002 CY - Berlin, BAM, Germany DA - 2002-09-11 PY - 2002 N1 - Geburtsname von Rosenthal, Martina: Scharmach, M. - Birth name of Rosenthal, Martina: Scharmach, M. SP - 1 EP - 9 AN - OPUS4-2018 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Müller, Christina A1 - Ewert, Uwe A1 - Rosenthal, Martina A1 - Bär, Sylke A1 - Schafer, Lloyd A1 - Völker, J. A1 - Wilrich, Peter-Th. T1 - Current status in the area of reliability of non-destructive testing and demining: Experience in Europe and USA T2 - Reliability and Diagnostics of Transport Structures and Means, Pardubice - Czech Republic CY - Pardubitz, Tschechische Republik DA - 2002-09-26 KW - Reliability of NDE Systems KW - Performance Demonstration KW - Essential Parameters KW - European Standards KW - Radiographic Testing KW - Film Digitalization KW - Austenitic Tube Welds KW - ROC KW - POD PY - 2002 SN - 80-7194464-5 SP - 1 EP - 14(?) PB - Univ. CY - Pardubice AN - OPUS4-2011 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -