A Likert Scale is a psychometric scale commonly used in questionnaires, and is the most widely used scale in survey research, such that the term is often used interchangeably with rating scale even though the two are not synonymous. When responding to a Likert questionnaire item, respondents specify their level of agreement to a statement. The scale is named after its inventor, psychologist Rensis Likert.
Instead of giving the respondent a dichotomous question with the only options being “yes” or “no,” Likert scales contain degrees of feeling (usually 5 or 7), so a more accurate response can be attained. Further, qualitative attributes such as feelings and emotions can be quantified and statistically analyzed.
Now, what exactly are the differences between Unipolar Likert Scale and Bipolar Likert Scale?
Unipolar Likert Scale
Unipolar scales are more contoured, allowing users to instead focus on the absence or presence of a single item. The scale measures the ordinal data, but most of the times unipolar scales generate more accurate answers. An example of a unipolar satisfaction scale is: not at all satisfied, slightly satisfied, moderately satisfied, very satisfied, and completely satisfied. A unipolar Likert scale question type indicates a respondent to think of the presence or absence of a quality. For example, a common unipolar scale includes the following choices: not at all satisfied, slightly satisfied, moderately satisfied, very satisfied, and completely satisfied. It is arranged on a 5 point scale. A to E. Also, Unipolar question types lend themselves where there is a maximum amount of the attitude or none of it. For instance, let’s say, how helpful was the apple pie recipe? Very helpful, somewhat or not at all. From there, we can safely assume there is something in between–like “sort of” helpful.
Bipolar Likert Scale
A bipolar scale indicates a respondent to balance two different qualities, defining the relative proportion of those qualities. Where a unipolar scale has one “pole,” a bipolar scale has two polar opposites. For example, a common bipolar scale includes the following choices: completely dissatisfied, mostly dissatisfied, somewhat dissatisfied, neither satisfied nor dissatisfied, somewhat satisfied, mostly satisfied, and completely satisfied. That is a scale with 0 in the middle (-3, -2, -1, 0, 1, 2, 3).