The response scale for the intellectual disability module of the WHOQOL: 5-point or 3-point?
Use a 3-point Likert scale instead of 5 when you ask clients with intellectual disability about quality of life.
01Research in Context
What this study did
The team compared two ways to ask adults with intellectual disability about their quality of life. One form used a 5-point smiley-face scale. The other used a simpler 3-point scale. They looked at which scale gave cleaner, more trustworthy answers.
What they found
The short 3-point scale won. Answers lined up in the expected order more often. The scale stayed reliable and kept its meaning, while the 5-point version did not.
How this fits with other research
Finney et al. (1995) warned that people with ID often say “yes” to anything. They urged simpler either/or questions plus pictures. The new study keeps that spirit but shows even a 3-point Likert works if you keep it short.
Embregts (2000) found the Child Behavior Checklist loses reliability when used with youth who have mild ID. That warning pairs well with the current finding: long, fine-grained scales can break down in this population.
Dababnah et al. (2025) later showed that any scale can drift over time. So pick the cleanest format first—here, the 3-point—and then re-check it each year.
Why it matters
If you run happiness or preference assessments, swap your 5-point faces for 3. You will spend less time explaining and still get data you can trust. One practical cut: keep the happy, neutral, and sad faces; drop the slightly-happy and slightly-sad ones. Your clients will answer faster and acquiesce less.
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02At a glance
03Original abstract
OBJECTIVE: To deal with the question of whether a 5-point response Likert scale should be changed to a 3-point scale when used in the field testing of people with intellectual disabilities (IDs), which was raised after the pilot study of World Health Organization Quality of Life (WHOQOL)-DIS, a module being developed with the World Health Organization measure of quality of life for disabilities. METHODS: Three possible ways were used to generate hypothetical data by merging a 5-point scale into a 3-point scale. The analyses were based on both item response theory and classical measurement theory. The partial credit model for polytomous response was performed for item evaluation; the confirmatory factor analysis was used to check construct validity, the Cronbach's alpha for domain reliability, and correlation analyses for the relationship between the 5-point scale and the generated 3-point scale. RESULTS: Most items with a 5-point response scale had disordered response options and/or unequal-length intervals between successive response options; these deficiencies were removed or improved without decline of validity and reliability in the hypothetical data of 3-point scales. CONCLUSION: Instead of the 5-point scale, a 3-point scale could be used for IDs in the field test of developing the module WHOQOL-DIS.
Journal of intellectual disability research : JIDR, 2011 · doi:10.1111/j.1365-2788.2011.01401.x