IPSATIVE AND NORMATIVE SCALES IN ADJECTIVAL MEASUREMENT OF PERSONALITY - PROBLEMS OF BIAS AND DISCREPANCY

887 respondents completed ipsative and normative versions of the PAL-T OPAS personality questonnaire. Data were analysed to test for (1) syst ematic bias in scores associated with the two response formats and (2) predictors of the magnitude of the discrepancy in the individual's ip sative and normative scores. Discrepancy was assessed for both item re sponses and scale scores. Sources of biases investigated included ipsa tive scaling artifact, extremeness of scores on the normative scales a nd response variability. Results showed that systematic bias in scale scores and magnitude of discrepancy were predicted by different factor s. One source of systematic bias was associated with ipsative scaling artifact: the ipsative scales measure both the scale itself and reject ion of other alternatives. A second source of systematic bias was acqu iescence in response to normative items. A confirmatory factor analysi s showed that a good but imperfect fit to the data may be obtained by constructing a structural model of the inter-relationship between norm ative and ipsative scores which accommodates both sources of bias. The strongest influence on discrepancy in scale scores was extremeness of normative scoring, associated with a bias towards either general acce ptance or rejection of trait adjectives. It is concluded that both nor mative and ipsative response formats have limitations, and it may ofte n be desirable to assess both.