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Psychological tests typically include a response scale whose purpose it is to organize and constrain the options available to respondents and facilitate scoring. One such response scale is the Likert scale, which initially was introduced to have a specific 5-point form. In practice, such scales have varied considerably in the nature and number of response options. However, relatively little consensus exists regarding several questions that have emerged regarding the use of Likert-type items. First, is there a "psychometrically optimal" number of response options? Second, is it better to include an even or odd number of response options? Finally, do visual analog items offer any advantages over Likert-type items? We studied these questions in a sample of 1,358 undergraduates who were randomly assigned to groups to complete a common personality measure using response scales ranging from 2 to 11 options, and a visual analog condition. Results revealed attenuated psychometric precision for response scales with 2 to 5 response options; interestingly, however, the criterion validity results did not follow this pattern. Also, no psychometric advantages were revealed for any response scales beyond 6 options, including visual analogs. These results have important implications for psychological scale development. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
Simms et al. (Thu,) studied this question.