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Seemingly minor changes to a questionnaire can make a big difference to mean scores: a cautionary tale

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Abstract

Background

It is not unusual for researchers to make apparently minor modifications to existing instruments without checking if this alters psychometric properties.

Method

Equivalent items on child mental health from two different versions of the Rutter parent questionnaire were compared: items from the standard version and from a modified version. The parents of 400 children aged 5–7 years were randomised into two groups: each group completed one version of the Rutter as well as an independent measure of psychopathology (the Strengths and Difficulties Questionnaire; SDQ).

Results

The mean psychopathology scores of the two groups were comparable according to the SDQ but differed markedly between the two Rutter versions, principally because of changes in the response categories. Nevertheless, the validity of the two versions of the Rutter was similar as judged from Rutter-SDQ correlations.

Conclusion

Seemingly minor changes in the wording of a measure can have a major impact on mean scores, thereby making it harder to compare or combine the results of studies using the original and the modified measure.

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Author information

Authors and Affiliations

  1. King’s College London, Institute of Psychiatry, London, UK

    Robert Goodman

  2. MRC Social, Genetic, and Developmental Psychiatry Centre, King’s College London, Institute of Psychiatry, London, UK

    Alessandra C. Iervolino, Stephan Collishaw & Barbara Maughan

  3. School of Epidemiology and Health Science, Centre for Census and Survey Research, University of Manchester, Manchester, UK

    Andrew Pickles

Authors
  1. Robert Goodman
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  2. Alessandra C. Iervolino
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  3. Stephan Collishaw
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  4. Andrew Pickles
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  5. Barbara Maughan
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Corresponding author

Correspondence to Robert Goodman.

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Goodman, R., Iervolino, A.C., Collishaw, S. et al. Seemingly minor changes to a questionnaire can make a big difference to mean scores: a cautionary tale. Soc Psychiat Epidemiol 42, 322–327 (2007). https://doi.org/10.1007/s00127-007-0169-0

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  • DOI: https://doi.org/10.1007/s00127-007-0169-0

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