validity The extent to which a measurement actually measures what it purports to measure or an entity actually is what it purports to be. There are several kinds of validity. Criterion validity is the extent to which a measured variable or an entity correlates with an external criterion of the phenomenon under study. This has two aspects: concurrent validity means that the measurement and the criterion refer to the same time and place; predictive validity is the ability to predict the criterion. Construct validity is the extent to which measurements conform to theoretical concepts or constructs. Content validity is the extent to which measurements incorporate the domain of the phenomenon under study. Study validity is the degree to which the inferences from a scientific study are warranted, taking into account the strengths and weaknesses of the study design. This has two aspects: internal validity, the degree to which observations may be attributed solely to the hypothesized effect that is being studied, and external validity, which is the extent to which the findings of a study can be generalized.
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"validity" A Dictionary of Public Health. Ed. John M. Last, Oxford University Press, 2007. Oxford Reference Online. Oxford University Press. Copenhagen University Library. 13 February 2008 http://www.oxfordreference.com/views/ENTRY.html?subview=Main&entry=t235.e4676
reliability Syn: reproducibility. The characteristic by which a measuring instrument or procedure yields a series of identical or closely similar measurements of the same variable that is repeatedly measured by the same observer using the same instrument or procedure. See also replication and reproducibility.
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"reliability" A Dictionary of Public Health. Ed. John M. Last, Oxford University Press, 2007. Oxford Reference Online. Oxford University Press. Copenhagen University Library. 13 February 2008 http://www.oxfordreference.com/views/ENTRY.html?subview=Main&entry=t235.e3869
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replication 1. The process of repeating an experiment or observation, perhaps many times, by different observers, to confirm or refute findings of original experiments or observations. It is an important property of all sound science that experiments and observations can be replicated, to help establish validity of observations and conclusions, conforming to the scientific criterion of reproducibility. It is a sine qua non of good scientific practice to make full details of research protocols readily available, to facilitate replication by other scientists.
2. In virology, replication is the multiplication of organisms.
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"replication" A Dictionary of Public Health. Ed. John M. Last, Oxford University Press, 2007. Oxford Reference Online. Oxford University Press. Copenhagen University Library. 13 February 2008 http://www.oxfordreference.com/views/ENTRY.html?subview=Main&entry=t235.e3879
reproducibility The quality of an experiment or test wherein repetition under identical or similar circumstances gives the same or a closely similar result to that achieved on the first occasion. See also reliability and repeatability.
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"reproducibility" A Dictionary of Public Health. Ed. John M. Last, Oxford University Press, 2007. Oxford Reference Online. Oxford University Press. Copenhagen University Library. 13 February 2008 <http://www.oxfordreference.com/views/ENTRY.html?subview=Main&entry=t235.e3882>
