Reliability

The two most important properties of an assessment are its validity and reliability. Validity refers to the meaningfulness of the interpretations and uses of a test score and is the most important property of an assessment. Reliability refers to the extent to which test scores are free from errors of measurement. Thus, validity examines the interpretations and uses that can reasonably be made from the consistent part of the test scores, whereas reliability is concerned with inconsistent or random errors of measurement. As a result, reliability is a necessary but not sufficient [Page 847]condition for validity. That is, there needs to be some level of consistency to understand the meaningfulness of particular uses and interpretations of test scores, but measuring consistently does not guarantee the ...