Steven Beackon's ‘Labour Party Politics and the Working Class’ (this Journal, VI (1976), 231–8) highlights a common problem in political science research, an inadequate concern for the validity of measuring instruments.

On the basis of six statements, the first three of which are claimed to be of an explicitly class character whilst the other three are not, Beackon classifies Labour party activists into those who perceived the party as a class party and those who did not. The weak discriminatory power of these statements is evidenced by their failure to assign fully 39 per cent of the respondents to either category. This third group of activists was labelled ‘Ambivalents’. An assessment of the measuring instrument's face validity, however, suggests that this ambivalence is due not so much to these activists' ambiguous perceptions of the party as to the shortcomings of the instrument itself.