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interviews, with the consequence that they would be unable to collect reliabledata on the phenomenon. Similarly, in the case of content analysis it isnecessary for the researcher to develop a category system in which the centraldenotative components of the concept alienation have been accounted for,before it is possible to analyze newspaper reports or letters to newspapers.Measurement validityIt is clear that an important question at this stage is: When are the operationalizationsof concepts or constructs valid? When does an operationalizationcomply with the requirement of measurement validity. In the field ofmeasurement theory it has become customary to distinguish amongst a numberof types of measurement validity which are presented schematically:MEASUREMENT VALIDITYCriterion validityConstruct validityFree download from www.hsrcpress.ac.zaconcurrentvaliditypredictivevalidityGiven the fact that there are numerous introductory texts in the field ofmeasurement theory (see list at the end of this chapter), brief descriptions ofeach concept will have to suffice.CRITERION VALIDITYAccording to Nunnally we refer to criterion validity when the purpose is to usean instrument to estimate some important form of behavior that is external tothe measuring instrument itself, the latter being referred to as the criterion(1978: 87). An example from everyday life is when we use the number ofdistinctions attained by matriculants as a predictor of academic achievement atuniversity. If a high positive correlation were to be found between number ofdistinctions and academic achievement, the former may justifiably be regardedas a good predictor of the latter.This is an example of predictive validity — the criterion which is employed todetermine whether the measurement is valid is situated in the future. If, in theexample of alienation, it were possible to develop criteria of the67