Internal construct validity of the Warwick-Edinburgh Mental Well-being Scale (WEMWBS): a Rasch analysis using data from the Scottish Health Education Population Survey
Stewart-Brown, Sarah L., Tennant, Ruth, Tennant, Alan, Platt, Stephen, Parkinson, Jane and Weich, Scott. (2009) Internal construct validity of the Warwick-Edinburgh Mental Well-being Scale (WEMWBS): a Rasch analysis using data from the Scottish Health Education Population Survey. Health and Quality of Life Outcomes, Vol.7 (No.15). ISSN 1477-7525
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Official URL: http://dx.doi.org/10.1186/1477-7525-7-15
Background: The Warwick-Edinburgh Mental Well-Being Scale (WEMWBS) was developed to meet demand for instruments
to measure mental well-being. It comprises 14 positively phrased Likert-style items and fulfils classic criteria for scale development. We report here the internal construct validity of WEMWBS from the perspective of the Rasch measurement model.
Methods: The model was applied to data collected from 779 respondents in Wave 12 (Autumn 2006) of the Scottish Health
Education Population Survey. Respondents were aged 16–74 (average 41.9) yrs.
Results: Initial fit to model expectations was poor. The items 'I've been feeling good about myself', 'I've been interested in new things' and 'I've been feeling cheerful' all showed significant misfit to model expectations, and were deleted. This led to a marginal improvement in fit to the model. After further analysis, more items were deleted and a strict unidimensional seven item scale (the Short Warwick Edinburgh Mental Well-Being Scale (SWEMWBS)) was resolved. Many items deleted because of misfit with
model expectations showed considerable bias for gender. Two retained items also demonstrated bias for gender but, at the
scale level, cancelled out. One further retained item 'I've been feeling optimistic about the future' showed bias for age. The correlation between the 14 item and 7 item versions was 0.954. Given fit to the Rasch model, and strict unidimensionality, SWEMWBS provides an interval scale estimate of mental well-being.
Conclusion: A short 7 item version of WEMWBS was found to satisfy the strict unidimensionality expectations of the Rasch model, and be largely free of bias. This scale, SWEMWBS, provides a raw score-interval scale transformation for use in parametric procedures. In terms of face validity, SWEMWBS presents a more restricted view of mental well-being than the 14 item WEMWBS, with most items representing aspects of psychological and eudemonic well-being, and few covering hedonic well-being or affect. However, robust measurement properties combined with brevity make SWEMWBS preferable to WEMWBS at present for monitoring mental well-being in populations. Where face validity is an issue there remain arguments for continuing to collect data on the full 14 item WEMWBS.
|Item Type:||Journal Article|
|Subjects:||B Philosophy. Psychology. Religion > BF Psychology|
|Divisions:||Faculty of Medicine > Warwick Medical School > Mental Health and Wellbeing
Faculty of Medicine > Warwick Medical School
|Library of Congress Subject Headings (LCSH):||Mental health -- Scotland, Mental health surveys -- Scotland, Rasch models -- Scotland|
|Journal or Publication Title:||Health and Quality of Life Outcomes|
|Publisher:||BioMed Central Ltd.|
|Official Date:||19 February 2009|
|Access rights to Published version:||Open Access|
World Health Organisation: Promoting Mental Health; Concepts emerging evidence and practice. In Summary report. Geneva; World Health Organisation; 2004.
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