Method of Summated Ratings: The Likert Scale
The Likert scale is an extremely popular means for measuring attitudes.
With the Likert scale, respondents indicate their attitudes by checking how strongly they
agree or disagree with carefully constructed statements, ranging from very positive to
very negative attitudes toward some object.
Individuals generally choose from approximately five (although alternatives may range
from three to nine) response alternatives: “strongly agree,” “agree,” “uncertain,”
“disagree,” and “strongly disagree.”
Researchers assign scores, or weights, to each possible response (e.g., 1, 2, 3, 4, and 5
assigned to each level of agreement).
Reverse Recoding
If a statement is framed negatively, the numerical scores would need to be reversed.
This is done by reverse coding the negative item so that a strong agreement really
indicates an unfavorable response rather than a favorable attitude.
In the case of a 5-point scale, recoding would make the value 1 equal to a new value
of 5, 2 equal to 4, 3 equal to 3, 4 equal to 2, and 5 equal to 1.
SPSS has a recode function.
Alternatively, for a 5-point scale, a simple mathematical formula can be entered:
Xnew value = 6 – Xold value
Composite Scales
A Likert scale may include several scale items to form a composite scale.
Each statement is assumed to represent an aspect of a common attitudinal domain.
The total score is the summation of the numerical scores assigned to an individual’s
responses.
In Likert’s original procedure, a large number of statements are generated, and an
item analysis is performed to eliminate those that are poor because they lack clarity
or elicit mixed response patterns.
Scales that use multiple items can be analyzed for reliability and validity.
Semantic Differential
The semantic differential is actually a series of attitude scales.
This popular attitude measurement technique consists of getting respondents to react to
some concept using a series of 7-point bipolar rating scales.
Bipolar adjectives—such as “good” and “bad,” “modern” and “old-fashioned,” or “clean”
and “dirty”—anchor both ends (or poles) of the scale.
The subject makes repeated judgments of the concept under investigation on each of the
scales.
Business researchers have found the semantic differential versatile and useful in business
applications.
The validity of the semantic differential depends on finding scale anchors that are
semantic opposites, which can sometimes prove difficult.
For scoring purposes, a numerical score is assigned to each position on the rating scale
(i.e., 1, 2, 3, 4, 5, 6, 7 or -3, -2, -1, 0, +1, +2, +3).