PhD ceremony Mr. D. Brouwer: Modern psychometric perspectives on the evaluation of clinical scales

PhD ceremony: Mr. D. Brouwer, 14.30 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Modern psychometric perspectives on the evaluation of clinical scales

Promotor(s): prof. R.R. Meijer

Faculty: Behavioural and Social Sciences

Clinical psychologists use questionnaires to measure the psychological functioning of their clients. Usually clients complete these questionnaires before treatment, and sometimes during and after treatment to measure the therapy progress. The psychological constructs that are measured, such as how hopeful or depressed a person is or how a person functions in social relationships, are often complex by nature and therefore difficult to measure. Psychometricians construct and evaluate these questionnaires and develop methods and theories of measurement.

In this thesis I demonstrate that modern psychometric methods provide valuable tools to investigate the quality of clinical questionnaires that we use in every day practice to measure and track the psychological functioning of our patients. First, I show that dividing questionnaires into different dimensions and subscales, which is common practice, can hardly be justified. I advise clinical psychologists to be critical and careful when they interpret subscales scores. Second, I observe that psychologists and policy makers are increasingly interested in measuring the progress of their clients during treatment with routine outcome monitoring applications. Results show that the reliabilities of scores can be different across measurements and that clinical screening questionnaires, that are often used in practice, can’t be readily used to measure individual change.