Optimal number of response categories in rating scales: reliability, validity, discriminating power, and respondent preferences

Acta Psychol (Amst). 2000 Mar;104(1):1-15. doi: 10.1016/s0001-6918(99)00050-5.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Female
  • Humans
  • Male
  • Observer Variation
  • Psychological Tests / standards*
  • Psychometrics
  • Reproducibility of Results
  • Surveys and Questionnaires / standards*