The stability of the symptom groupings in the Inpatient Multidimensional Psychiatric Scale (IMPS).

A full set of data has been gathered on admission of 1654 inpatients and included information on all 90 items from the Inpatient Multidimensional Psychiatric Scale (IMPS). The sample was divided into two by means of an odd-even split and principal component analyses with Varimax rotation as well as Ward hierarchical cluster analyses of symptoms were run on both subsamples. Comparisons of results were than made between the two subsamples, between the two methods of analysis, and with the studies of Lorr and Klett and Behrends et al. In general, earlier results concerning the structure of the symptom groupings have been confirmed. However, by comparing all the different sets of results, those symptom groupings that are particularly stable or unstable have been identified. In addition, comparisons have been made between the results from analyses using the full range of scores on the items and those using dichotomized scores in order to determine whether the use of different rating scales for different items has an effect on the resulting item groupings.