How we change what others think, feel, believe and do
The Likert Scale is an ordered, one-dimensional scale from which respondents choose one option that best aligns with their view.
There are typically between four and seven options. Five is very common (see arguments about this below).
All options usually have labels, although sometimes only a few are offered and the others are implied.
A common form is an assertion, with which the person may agree or disagree to varying degrees.
In scoring, numbers are usually assigned to each option (such as 1 to 5).
5-point traditional Likert scale:
5-point Likert-type scale, not all labeled:
6-point Likert-type scale:
Questions may be selected by a mathematical process, as follows:
The Likert scale is named after its originator, Rensis Likert.
A benefit is that questions used are usually easy to understand and so lead to consistent answers. A disadvantage is that only a few options are offered, with which respondents may not fully agree.
As with any other measurement, the options should be a carefully selected set of questions or statements that act together to give a useful and coherent picture.
A problem can occur where people may become influenced by the way they have answered previous questions. For example if they have agreed several times in a row, they may continue to agree. They may also deliberately break the pattern, disagreeing with a statement with which they might otherwise have agreed. This patterning can be broken up by asking reversal questions, where the sense of of the question is reversed - thus in the example above, a reversal might be 'I do not like going to Chinese restaurants'. Sometimes the 'do not' is emphasized, to ensure people notice it, although this can cause bias and hence needs great care.
There is much debate about how many choices should be offered. An odd number of choices allows people to sit on the fence. An even number forces people to make a choice, whether this reflects their true position or not.
Some people do not like taking extreme choices as this may make them appear as if they are totally sure when they realize that there are always valid opposing views to many questions. They may also prefer to be thought of as moderate rather than extremist. They thus are much less likely to choose the extreme options. This is a good argument to offer seven choices rather than five. It is also possible to note people who do not make extreme choices and 'stretch' their scores, although this can be a somewhat questionable activity.
[For these reasons, I have a personal preference for six options].
There is also debate as to what is a true Likert scale and what is a 'Likert-type' scale. Likert's original scale (in his PhD thesis) was bipolar, with five points running from one extreme to another, through a neutral central position, ranging from 'Strongly Agree' to 'Strongly Disagree'.
The Likert scale is also called the summative scale, as the result of a questionnaire is often achieved by summing numerical assignments to the responses given.
Likert, R. (1932). A Technique for the Measurement of Attitudes, Archives of Psychology, No.140