The meaning of vaguely quantified frequency response options on a quality of life scale depends on respondents’ medical status and age
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Self-report items in quality of life (QoL) scales commonly use vague quantifiers like “sometimes” or “often” to measure the frequency of health-related experiences. This study examined whether the meaning of such vaguely quantified response options differs depending on people’s medical status and age, which may undermine the validity of QoL group comparisons.
Respondents (n = 600) rated the frequency of positive and negative QoL experiences using vague quantifiers (never, rarely, sometimes, often, always) and provided open-ended numeric frequency counts for the same items. Negative binomial regression analyses examined whether the numeric frequencies associated with each vague quantifier differed between medical status (no vs. one or more medical conditions) and age (18–40 vs. 60+ years) groups.
Compared to respondents without a chronic condition, those with a medical condition assigned a higher numeric frequency to the same vague quantifiers for negative QoL experiences; this effect was not evident for positive QoL experiences. Older respondents’ numeric frequencies were more extreme (i.e., lower at the low end and somewhat higher at the high end of the response range) than those of younger respondents. After adjusting for these effects, differences in QoL became somewhat more pronounced between medical status groups, but not between age groups.
The results suggest that people with different medical backgrounds and age do not interpret vague frequency quantifiers on a QoL scale in the same way. Open-ended numeric frequency reports may be useful to detect and potentially correct for differences in the meaning of vague quantifiers.
KeywordsQuality of life Chronic illness Age Frequency ratings Vague quantifiers Self-report
We would like to thank Joan Broderick, PhD, Doerte Junghaenel, PhD, and Alicia Bolton, PhD, for helpful discussions in preparation of this manuscript.
This work was supported by a grant from the National Institute on Aging (R01 AG042407).
Compliance with ethical standards
Conflict of interest
Stefan Schneider declares that he has no conflict of interest. Arthur A. Stone is a Senior Scientist with the Gallup Organization.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
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