Rating scale

A rating scale quantifies responses to items or questions in a test, survey or questionnaire using a set of categories. These categories may take a number of formats, such as an ordered series of numbers, e.g. 1 to 4; a series of descriptions: “strongly disagree” to “strongly agree”; or a combination of the two. It is also possible to have a rating scale consisting of a series of numbers with two qualitative descriptors (known as “anchors”), one at each extreme. Where only qualitative descriptors are used, these will be assigned a numerical value for scoring purposes. There are no limits to how many categories can be included in a rating scale but scales with 4, 5, 7 and 10 categories are commonly used. Responses to rating scales for a number of test items may be summed to produce sub-total (“domain”) or overall scores. In the latter case, this is known as a Likert scale. The majority of rating scales are ordinal: although the categories increase monotonically, the distances between each category cannot be assumed to be equal. For example, if “disagree” is assigned the value 2, “agree” a 3 and “strongly agree” a 4, the difference between “strongly agree” and “agree” cannot be assumed to be the same as the difference between “agree” and “disagree”.