Abstract
Objectives
In studies involving theoretical constructs, it is important that measures have good content validity and that there is not contamination of measures by content from other constructs. While reliability and construct validity are routinely reported, to date, there has not been a satisfactory, transparent, and systematic method of assessing and reporting content validity. In this paper, we describe a methodology of discriminant content validity (DCV) and illustrate its application in three studies.
Methods
Discriminant content validity involves six steps: construct definition, item selection, judge identification, judgement format, single-sample test of content validity, and assessment of discriminant items. In three studies, these steps were applied to a measure of illness perceptions (IPQ-R) and control cognitions.
Results
The IPQ-R performed well with most items being purely related to their target construct, although timeline and consequences had small problems. By contrast, the study of control cognitions identified problems in measuring constructs independently. In the final study, direct estimation response formats for theory of planned behaviour constructs were found to have as good DCV as Likert format.
Conclusions
The DCV method allowed quantitative assessment of each item and can therefore inform the content validity of the measures assessed. The methods can be applied to assess content validity before or after collecting data to select the appropriate items to measure theoretical constructs. Further, the data reported for each item in AppendixS1 can be used in item or measure selection.
Original language | English |
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Pages (from-to) | 240-257 |
Number of pages | 18 |
Journal | British Journal of Health Psychology |
Volume | 19 |
Issue number | 2 |
Early online date | 15 Mar 2014 |
DOIs | |
Publication status | Published - 1 May 2014 |
Keywords
- theory
- psychometrics
- measurement
- content validity
- questionnaires
- validity
- illness perception questionnaire
- social cognitive theory
- planned behavior
- confounded measures
- perceived control
- past behavior
- chronic pain
- perspective
- models
- disability