While the abstract concept of validity makes sense, actual testing for validity can be challenging. Because validity exists on a continuum, with degrees of less and more valid, we think of some tools as being more valid than others. This means that a test to determine which tools are most or least valid can be useful.

While the abstract concept of validity makes sense, actual testing for validity can be challenging. Because validity exists on a continuum, with degrees of less and more valid, we think of some tools as being more valid than others. This means that a test to determine which tools are most or least valid can be useful.