Optimal number of response categories in rating scales: reliability, validity, discriminating power, and respondent preferences.
Using a self-administered questionnaire, 149 respondents rated service elements associated with a recently visited store or restaurant on scales that differed only in the number of response categories (ranging from 2 to 11) and on a 101-point scale presented in a different format. On several indices of reliability, validity, and discriminating power, the two-point, three-point, and four-point scales performed relatively poorly, and indices were significantly higher for scales with more response categories, up to about 7. Internal consistency did not differ significantly between scales, but test-retest reliability tended to decrease for scales with more than 10 response categories. Respondent preferences were highest for the 10-point scale, closely followed by the seven-point and nine-point scales. Implications for research and practice are discussed.
Preston
C C
CC
Department of General Practice and Primary Health Care, University of Leicester, UK.
Colman
A M
AM
D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D011581:Psychological Tests / Q000592:standards*; D011594:Psychometrics; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards*