Test Reliability and Validity Defined
Test reliablility refers to the degree to which a test is consistent and stable in measuring what it is intended to measure. Most simply put, a test is reliable if it is consistent within itself and across time. To understand the basics of test reliability, think of a bathroom scale that gave you drastically different readings every time you stepped on it regardless of whether your had gained or lost weight. If such a scale existed, it would be considered not reliable.
Test validity refers to the degree to which the test actually measures what it claims to measure. Test validity is also the extent to which inferences, conclusions, and decisions made on the basis of test scores are appropriate and meaningful. The 2000 and 2008 studies present evidence that Ohio's mandated accountability tests are not valid, that the conclusions and decisions that are made on the basis of OPT performance are not based upon what the test claims to be measuring.
The Relationship of Reliability and Validity
Test validity is requisite to test reliability. If a test is not valid, then reliability is moot. In other words, if a test is not valid there is no point in discussing reliability because test validity is required before reliability can be considered in any meaningful way. Likewise, if as test is not reliable it is also not valid. Therefore, the two Hoover Studies do not examine reliability.