Clinical Assessment of Child and Adolescent Personality and ...

CHAPTER 2 MEASUREMENT ISSUES39administered to a group of children, and thensometime in the future- perhaps two months,three months, or even six years-a criterionmeasure (such as clinicians’ ratings of adjustment)is administered to the same group ofchildren (see Verhulst et al., 1994).Correlations with Other TestsOne can use correlations with other teststo evaluate the validity of a behavior orpersonality test. In a sense, this method isa special type of concurrent validity study.The difference is that the correlation is notbetween a personality measure and somecriterion variable, such as clinicians’ ratingsof adjustment, but between a personalitytest and a measure of the same construct,another personality measure. For example,if a new test of anxiety is published, itshould show a substantial relationship withprevious measures, but not an extremelyhigh relationship (Anastasi & Urbina,1998). If a new personality test correlates.99 with a previous personality test, then itis not needed, as it is simply another formof an existing test and does not contributeto increasing our understanding of the constructof personality. If a new anxiety scalecorrelates only .15 with existing well-validatedanxiety scales, it is also likely not tobe a good measure of personality. New personalitytests should show a moderate tostrong relationship with existing tests, yetcontribute something new to our understandingof the construct of interest.Convergent/Discriminant ValidityConvergent validity is established when ascale correlates with constructs with which itis hypothesized to have a strong relationship.Discriminant validity is supported when apersonality measure has a poor correlationwith a construct with which it is hypothesizedto be unrelated. These types of validitymay be important to consider if there are noexisting, well-normed, or relatively recentmeasures of a construct. That is, one may notbe able to judge the criterion-related validityof a measure because no other suitable measuresof that particular construct exist. Ofcourse, convergent and discriminant validityare important indicators of validity for existing/establishedmeasures as well.If one were assessing the convergentand discriminant validity of a measure ofanxiety, one would expect high correlationswith other measures of anxiety andmoderate correlations with other measuresof depression, given the well documentedassociation between anxiety and depression(Klein et al., 2005). However, one wouldexpect only minimal correlations betweenanxiety and measures of learning problems,thus providing support for its divergentvalidity.Factor AnalysisFactor analysis is a popular technique forvalidating modern tests of personality thattraces its roots to the work of the eminentstatistician Karl Pearson (1901). Factoranalysis has become increasingly popularas a technique for test validation. A wealthof factor-analytic studies dates to the 1960swhen computers became available. Factoranalysis is difficult to explain in only a fewparagraphs. Those readers who are interestedin learning factor analysis need a separatecourse on this technique and a greatdeal of independent reading and experience.A thorough discussion of factor-analytictechniques can be found in Gorsuch(1988). An introductory-level discussioncan be found in Anastasi & Urbina (1998)and Kamphaus (2001).Factor analysis is a data reduction techniquethat attempts to explain variancein the most efficient way. Most scales oritems included in a test correlate with oneanother. It is theorized that this correlationis the result of one or more common factors.The purpose of factor analysis is toreduce the correlations between all scales