Deconstructing therapy outcome measurement with Rasch analysis of a measure of general clinical distress: the Symptom Checklist-90-Revised.
Rasch analysis was used to illustrate the usefulness of item-level analyses for evaluating a common therapy outcome measure of general clinical distress, the Symptom Checklist-90-Revised (SCL-90-R; Derogatis, 1994). Using complementary therapy research samples, the instrument's 5-point rating scale was found to exceed clients' ability to make reliable discriminations and could be improved by collapsing it into a 3-point version (combining scale points 1 with 2 and 3 with 4). This revision, in addition to removing 3 misfitting items, increased person separation from 4.90 to 5.07 and item separation from 7.76 to 8.52 (resulting in alphas of .96 and .99, respectively). Some SCL-90-R subscales had low internal consistency reliabilities; SCL-90-R items can be used to define one factor of general clinical distress that is generally stable across both samples, with two small residual factors.
Elliott
Robert
R
Counselling Unit, University of Strathclyde, Glasgow, Scotland. fac0029@gmail.com
Fox
Christine M
CM
Beltyukova
Svetlana A
SA
Stone
Gregory E
GE
Gunderson
Jennifer
J
Zhang
Xi
X
D000328:Adult; D001714:Bipolar Disorder / Q000175:diagnosis* / Q000523:psychology / Q000628:therapy; D003866:Depressive Disorder / Q000175:diagnosis* / Q000523:psychology / Q000628:therapy; D004192:Discrimination, Psychological / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D015233:Models, Statistical; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data*; D011594:Psychometrics / Q000379:methods; D011613:Psychotherapy / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D013315:Stress, Psychological / Q000175:diagnosis / Q000523:psychology / Q000628:therapy; D016896:Treatment Outcome