Ipsative and Normative Scales in Adjectival Measurement of Personality: Problems of Bias and Discrepancy

Abstract

887 respondents completed ipsative and normative versions of the PAL‐TOPAS personality questionnaire. Data were analysed to test for (1) systematic bias in scores associated with the two response formats and (2) predictors of the magnitude of the discrepancy in the individual's ipsative and normative scores. Discrepancy was assessed for both item responses and scale scores. Sources of biases investigated included ipsative scaling artifact, extremeness of scores on the normative scales and response variability. Results showed that systematic bias in scale scores and magnitude of discrepancy were predicted by different factors. One source of systematic bias was associated with ipsative scaling artifact: the ipsative scales measure both the scale itself and rejection of other alternatives. A second source of systematic bias was acquiescence in response to normative items. A confirmatory factor analysis showed that a good but imperfect fit to the data may be obtained by constructing a structural model of the inter‐relationship between normative 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 acceptance or rejection of trait adjectives. It is concluded that both normative and ipsative response formats have limitations, and it may often be desirable to assess both.