FIM levels as ordinal categories.

Data collected on rating scales have generally been analyzed without verifying that the scales have functioned as intended. The FIM levels are precisely conceptualized and meticulously defined. Their effective empirical functioning as ordinal categories merits continual monitoring. Ordinality implies that each succeeding level represents a higher level of functioning. Further, as a patient improves in functioning each ordinal level in turn is expected to be observed. Taking advantage of the clarity of Rasch theory, guidelines are suggested that prompt the analyst to investigate whether the rating categories are cooperating to produce observations on which useful measurement and prudent inference about patient status can be based.