The response scale for the intellectual disability module of the WHOQOL: 5-point or 3-point?

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 confirmato..