INDIVIDUAL-RESPONSE SPREAD IN SELF-REPORT SCALES - PERSONALITY CORRELATIONS AND CONSEQUENCES

We consider the phenomenon of individual differences in the use of que stionnaire scales and examine some of its consequences. Results from t wo illustrative studies on farmers and consultant doctors are used to demonstrate that individual standard deviation of response option usag e is a consistent trait which is significantly correlated with the per sonality dimension of conscientiousness. A mathematical model of indiv idual response spread is also devised and it is shown that significant spurious correlations between responses to independent items can aris e. This model is extended by estimating individual response thresholds from our two illustrative data sets; numerical simulation using these thresholds confirms the occurrence of spurious correlations. The dist ribution of correlation coefficients r is also very different from the standard form used for estimating levels of significance. There are w idespread consequences of these observations for standard multivariate methods of analysing self-report data. (C) 1998 Elsevier Science Ltd. All rights reserved.