GRAEME HAWTHORNE, HELEN HERRMAN and BARBARA MURPHY INTERPRETING THE WHOQOL-BRE ` F: PRELIMINARY POPULATION NORMS AND EFFECT SIZES (Accepted 1 November 2005) ABSTRACT. Since publication use of the WHOQOL-Bre`f has rapidly risen. However, as yet no population norms have been published as a reference point against which researchers can interpret their findings. This study provides preliminary population norms for this purpose. Randomly sampled community residents from two studies were pooled and used to examine the properties of the WHOQOL-Bre`f by age group, gender and health status. The results showed that general norms for the WHOQOL-Bre`f domains were 73.5 (SD=18.1) for the Physical health domain, 70.6 (14.0) for Psychological wellbeing, 71.5 (18.2) for Social relationships and 75.1 (13.0) for the Environment domain. In general scores declined slightly by age group. For females scores were stable across the lifespan with an accelerated decline after the age of 60 years. Males exhibited a more consistent and even decline across the lifespan. There were significant differences in WHOQOL-Bre`f scores when reported by health status, with those in poor health obtaining scores that were up to 50% lower than those in excellent health. Effect sizes between different health status levels are reported. These preliminary norms and effect sizes may be used as reference points for interpreting WHOQOL-Bre`f scores. They provide addi- tional information to the numerous national studies already reporting on the validity of the WHOQOL-Bre` f. KEY WORDS: effect sizes, population norms, profile health status instruments, quality of life measurement, WHOQOL-Bre` f 1. INTRODUCTION The past decade has seen increasing recognition of the importance of quality of life (QoL) as a crucial measure for describing subjective wellbeing (SWB) in population studies as well as being an outcome measure in clinical trials. Implicit in this recognition is that although social indicators (e.g. economic resources, gross domestic product) form the milieu within which individuals live, their QoL is determined by evaluation of their personal lives and social situation (Eckersley, 2000b). Thus measuring QoL provides the means by which the respondent’s perspective can be placed alongside traditional indi- cators such as economic growth or medical morbidity (Szabo and WHOQOL Group, 1996). However, a major limiting factor has been the lack of any Social Indicators Research (2006) 77:37–59 Ó Springer 2006 DOI 10.1007/s11205-005-5552-1