Hg. Dickson et F. Kohler, THE MULTIDIMENSIONALITY OF THE FIM MOTOR ITEMS PRECLUDES AN INTERVAL SCALING USING RASCH ANALYSIS, Scandinavian journal of rehabilitation medicine, 28(3), 1996, pp. 159-162
Rasch analysis scaling is said to produce an interval scale of Functio
nal Independence Measure (FIM) motor function items. Rasch analysis re
quires that the data to be analysed represent the influence of a singl
e underlying unidimensional variable. A unidimensional interval scale
of activities of daily living means that a person who can perform the
most difficult item on a scale can also perform the easiest item. For
a FIM motor function interval scale, the ability to climb stairs would
imply necessarily an ability to eat normally. As this need not be the
case, the FIM motor items do not constitute an adequate interval scal
e. Eating and walking are different activities, and a unidimensional c
onstruct linking them is unsatisfactory. A principal components analys
is of the admission FIM motor function items of 515 consecutive patien
ts admitted to an inpatient rehabilitation unit revealed that more tha
n one significant factor was necessary to explain the variance in scor
es. The counter-factual and statistical evidence argues that a unidime
nsional construct does not underly the FIM motor function items, and t
he use of Rasch analysis will not lead to a description of interval pr
operties of the FIM motor function items.