The Stapel scale is used as an alternative to the semantic differential, especially when it is difficult to find bipolar adjectives that match the investigative question.
The scale places a single adjective in the center of an even number of numerical values (for example, ranging from +3 to -3).
It measures how close or how distant from the adjective a given stimulus is perceived to be.
The table below illustrates a Stapel scale item used in the measurement of the attitude of the student toward a class teacher:
Respondents select a plus (+) number for the characteristic that describes the named teacher. The more accurate the description, the larger is the positive number.
Similarly, the less accurate the description, the larger is the negative number chosen. Ratings range from +3 to -3, very accurate to very inaccurate.
Like the semantic differential, Stapel scales produce interval data.