Asking Questions - The Definitive Guide To Questionnaire Design ...

ASKING QUESTIONS ABOUT ATTITUDES AND BEHAVIORS 127
but they all rely on the idea that a good scale has a high intercorrelation
of the items.
Another commonly used scale type is the Guttman scale, named
after Louis Guttman, another pioneer in attitude measurement.
Guttman’s approach was to devise questions that measured increasing
agreement (or disagreement) with attributes of the attitude
object. In contrast to the Likert model where the total number of
items agreed to without regard to their order is the measure of the
attitude, items in a Guttman scale are ordered such that some items
should be agreed to only by those who are low on the attitude and
others should be agreed to only by those who are high on the attitude
scale.
An example of the difference in approach applied to attitudes
about free speech is presented in abbreviated form in Figure 4.2.
The first format is that of the Likert scale. Several items are stated
in propositional form and respondents are asked to indicate the
degree of their agreement or disagreement with the statement. The
scale score is then determined by giving numerical values to the response
categories and adding up the values given to respondents’
responses.
The second format in Figure 4.2 is that of a Guttman scale. Here
the items are presented in an order of increasing commitment (or
opposition) to free speech. Various methods for combining responses
can be used. The simplest is to count the number of “yes” and “no”
answers as appropriate. Some decision would have to be made about
the “don’t knows.” One alternative is to leave them out or to treat
them as lying somewhere between the “yes” and “no” responses.
More complex treatments include giving more weight to the less frequent
responses or weighting the less frequent responses according
to some a priori view of the relationship between the content of the
hypothetical speech and the strength of a belief in freedom of expression.
Again we stress that you must make such decisions on the
basis of your research question and your conception of the measurement
model. Guttman scales are somewhat harder to develop and
thus are not so commonly used as Likert scales.