Likert scale was introduced to survey research in 1930. Scale name comes from Rensis Likert (1903 - 1981), an American psychologist, educator, and sociologist.
Likert scale is a bipolar scale with interval levels that measure respondent attitudes and opinions. "Bipolar" means that scale has two opposite poles, on each end of the scale one will find opposite opinions and attitudes. "Interval-level" means that points on the scale are ordered and the length between the points is equal (equidistant).
The most popular version of the Likert scale is 5-points scale.
5-point question example
Do you agree that SurveyLab online survey tool has a user-friendly interface?
- Strongly disagree
- Rather disagree
- Neither agree nor disagree
- Rather agree
- Strongly agree
5-point Likert scale can have so-called central tendency bias. People generally tend to select average points to radical ones (very high or very low). The consequence of this is a big number of answers with average (neutral) selections.
Another example of the Likert scale is 7-points scale.
7-point question example
Do you agree that SurveyLab allows users to create surveys easily?
- Strongly disagree
- Disagree
- Rather disagree
- Neither agree nor disagree
- Rather agree
- Agree
- Strongly agree
7-point Likert scale was introduced to increase accuracy of the measurement, thanks to introduction of two additional answer choices on each pole of the scale.