Causal Variables, Indicator Variables and Measurement Scales: An Example from Quality of Life

Summary There is extensive literature on the development and validation of multi-item measurement scales. Much of this is based on principles derived from psychometric theory and assumes that the individual items form parallel tests, so that simple weighted or unweighted summation is an appropriate method of aggregation. More recent work either continues to promulgate these methods or places emphasis on modern techniques centred on item response...