ABSTRACT
Most measures use additive scaling, indicating a concept of equivalence of items or activities. In these measures, failure on feeding, self-care or mobility would contribute in a similar manner to the overall score. Other measures such as the Sickness Impact Profile (SIP) (Bergner et aI., 1981) or Functional Limitations Profile (FLP) (Patrick & Peach, 1989) use weighted additive scores, where failure on some items counts for more than failure on other items; for example, difficulties in walking a long distance count for less than difficulties in walking a short distance. Williams et al. (1976) proposed that a cumulative hierarchical model was appropriate and used scaling methods that represented this model and others have adopted this approach (e.g. Whiting & Lincoln, 1980). Using this approach, the underlying theoretical model proposes that disabilities are acquired or lost in a systematic, ordered way; failure on an "easy" item then reflects both more disability and more severe disability.
