We are in the process of upgrading and improving our Assessment Centre product, the Competency Assessment Series (CAS). We are changing the number of response categories from 5 to 4. Here is some of the reasoning behind this change: "The choice of response scale is a critical aspect of psychological assessments which is often underemphasised in test development. Particularly the number of response categories remains an important design feature of psychometric assessments. In general two options are available: dichotomous (i.e. true-false or yes-no categories) and multichotonous (i.e. Likert types) scales. A primary advantage of using a multichotomous response scales relative to dichotomous scales is that they tend to create more scale variance. However, with multichotomous scales one should carefully consider the amount of scale points. The decision to use odd or even numbers is particularly important. Scales with odd-numbered response scales tend to provide respondents with “neutral" response options which is endorsed disproportional more than other scale categories. Reason being, odd numbered scales provides a "safe zone" for respondents which are used when respondents are reluctant or unmotivated to respond to scale stimuli. With the use of even numbered scale points, respondents are forced to have an opinion, or at least to indicate a weak commitment to what is being expressed in an item (Netemeyer, Bearden, & Sharma, 2003). For this reason – many scale developers prefer to utilise even-numbered multichotomous response scales.”
