A test can be considered an observation or experiment that determines one or more characteristics of a given sample, product, process, or service. The purpose of testing involves a prior determination of expected observation and a comparison of that expectation to what one actually observes. The results of testing can be qualitative (yes/no), quantitative (a measured value), or categorical and can be derived from personal observation or the output of a precision measuring instrument.
Usually the test result is the dependent variable, the measured response based on the particular conditions of the test or the level of the independent variable. Some tests, however, may involve changing the independent variable to determine the level at which a certain response occurs: in this case, the test result is the independent variable.
Using a standardized test method, perhaps published by a respected standards organization, is a good place to start. Sometimes it is more useful to modify an existing test method or to develop a new one, though such home-grown test methods should be validated and, in certain cases, demonstrate technical equivalency to primary, standardized methods. Again, documentation and full disclosure are necessary.
A well-written test method is important. However, even more important is choosing a method of measuring the correct property or characteristic. Not all tests and measurements are equally useful: usually a test result is used to predict or imply suitability for a certain purpose. For example, if a manufactured item has several components, test methods may have several levels of connections:
test results of a raw material should connect with tests of a component made from that material
Test methods are often scrutinized for their validity, applicability, and accuracy. It is very important that the scope of the test method be clearly defined, and any aspect included in the scope is shown to be accurate and repeatable through validation.
Test method validations often encompass the following considerations:
accuracy and precision; demonstration of accuracy may require the creation of a reference value if none is yet available
^"Form and Style for ASTM Standards". ASTM International. October 2017. Retrieved 8 February 2018.
^ abcdeCommittee E-11 on Quality Control of Materials (1963). ASTM Manual for Conducting an Interlaboratory Study of a Test Method. American Society for Testing and Materials. p. 3. Retrieved 8 February 2018.
^ abNigh, P.; Gattiker, A. (2000). Test method evaluation experiments and data. Proceedings from the International Test Conference, 2000. Vol. 2000. pp. 454–463. doi:10.1109/TEST.2000.894237. ISBN 978-0-7803-6546-9.
^ abcdeBridwell, H.; Dhingra, V.; Peckman, D.; et al. (2010). "Perspectives on Method Validation: Importance of Adequate Method Validation". The Quality Assurance Journal. 13 (3–4): 72–77. doi:10.1002/qaj.473.
^"Glossary: S–Z". Understanding Science. University of California Museum of Paleontology. Retrieved 8 February 2018.
^ ab"Why are these rest results so different?: The importance of testing methods in chemical and microbiological testing" (PDF). Asia Pacific Laboratory Accreditation Cooperation. January 2008. Retrieved 8 February 2018.
^ abcSnodgrass, B.; Grant, T.; McCallum, K.; et al. (26 July 2014). "ISO 17025 Accreditation/Quality Management Systems Panel Discussion" (PDF). Association of American Feed Control Officials. Retrieved 8 February 2018.
^Higgins, C. (2009). "Test Design and Documentation" (PPT). University of Nottingham. Retrieved 8 February 2018.
^ ab"Test Method, Validation and Verification of Methods: APHL Quality Management System (QMS) Competency Guidelines" (PDF). Association of Public Health Laboratories. Retrieved 8 February 2018.
^ abOffice of Regulatory Science (12 May 2014). "5.4 Test Methods and Method Validation" (PDF). Laboratory Manual Of Quality Policies For ORA Regulatory Laboratories: Volume 1. U.S. Food and Drug Administration. Retrieved 8 February 2018.
General references, booksEdit
Pyzdek, T, "Quality Engineering Handbook", 2003, ISBN 0-8247-4614-7
Godfrey, A. B., "Juran's Quality Handbook", 1999, ISBN 007034003X
Kimothi, S. K., "The Uncertainty of Measurements: Physical and Chemical Metrology: Impact and Analysis", 2002, ISBN 0-87389-535-5
ASTM E177 Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
ASTM E691 Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
ASTM E1488 Standard Guide for Statistical Procedures to Use in Developing and Applying Test Methods
ASTM E2282 Standard Guide for Defining the Test Result of a Test Method
ASTM E2655 - Standard Guide for Reporting Uncertainty of Test Results and Use of the Term Measurement Uncertainty in ASTM Test Methods