On tests of validity and social class: Why Prandy and Blackburn are wrong

The comment by Prandy and Blackburn (1997) on Evans's (1996a) recent paper in this journal raises a number of important issues: what does validation entail; what would the validation of the Goldthorpe class schema entail; and is validation 'logically unlikely' and 'in practice not possible'? Unfortunately, the proffered answers to these questions reveal a degree of confusion on the part of their authors, which is further amplified in Prandy and Blackburn's attempt to proselytise for their own measure, the 'Cambridge scale'. This paper will examine these issues, loosely grouped into sections on validity, the Cambridge scale, and issues of measurement, and demonstrate that: (i) Prandy and Blackburn appear to misunderstand what validity tests are intended to achieve; (ii) they similarly fail to understand what the Goldthorpe class schema is trying to measure and how it might therefore be validated; (iii) they are mistaken in their appraisal of some of the measurement issues in Evans's paper and engage in a misleading comparison of his findings with work of their own; and (iv) they overlook the evident uncertainty concerning what their own Cambridge scale measures.