validity & reliability
For the statistical consultant working with social science researchers the estimation of reliability and validity is a task frequently encountered. Measurement issues differ in the social sciences in that they are related to the quantification of abstract, intangible and unobservable constructs. In many instances, then, the meaning of quantities is only inferred.
Let us begin by a general description of the paradigm that we are dealing with. Most concepts in the behavioral sciences have meaning within the context of the theory that they are a part of. Each concept, thus, has an operational definition which is governed by the overarching theory. If a concept is involved in the testing of hypothesis to …show more content…
All in all we need to always keep in mind the contextual questions: what is the test going to be used for? how expensive is it in terms of time, energy and money? what implications are we intending to draw from test scores?
Research requires dependable measurement. (Nunnally) Measurements are reliable to the extent that they are repeatable and that any random influence which tends to make measurements different from occasion to occasion or circumstance to circumstance is a source of measurement error. (Gay) Reliability is the degree to which a test consistently measures whatever it measures. Errors of measurement that affect reliability are random errors and errors of measurement that affect validity are systematic or constant errors.
Test-retest, equivalent forms and split-half reliability are all determined through correlation.
Test-retest reliability is the degree to which scores are consistent over time. It indicates score variation that occurs from testing session to testing session as a result of errors of measurement. Problems: Memory, Maturation, Learning.
Equivalent-Forms or Alternate-Forms Reliability:
Two tests that are identical in every way except for the actual items included. Used when it is likely that test takers will