Reading research critically: assessing the validity and reliability of research instrumentation--Part 2.

Accurate measurement of research variables is necessary so that research consumers can trust that it is the research intervention that affected the change in the outcome variable, not some extraneous error component. Reliability is the accuracy with which the research instruments measure the variable that they are designed to measure. A number of known threats to instrument reliability should be anticipated by the researcher and looked for the consumer. These threats are presented in this article.