Scale Analysis

The Theory of Planned Behavior Questionnaire (TPB-42) was developed by Ajzen in 1985. It originated as the Theory of Reasoned Action in 1980, aiming to predict an individual’s intention to engage in a specific behavior at a particular time and place. The theory was intended to explain all behaviors over which people have the ability to exert self-control.

Scale Objective

The questionnaire was created to enhance the predictive ability of the Theory of Planned Behavior. It derives directly from this theory and assesses each of its core constructs: behavior, perceived norm, perceived behavioral control, and intention.

Question Calibration

Participants are asked to respond based on whether they agree or disagree with items related to behavioral beliefs, subjective normative beliefs, and perceptions of behavioral control. The questionnaire consists of 12 demographic questions and 42 items answered using a 7-point Likert scale ranging from 1 (Unlikely, no) to 7 (Likely, yes).

Statistical Analysis

The scale produces a total score by summing the responses to all items, with the range extending from 42 to 294. Higher scores indicate greater agreement with behavioral beliefs.

Validity and Reliability

The scale has been adapted into Greek by Theodorakis and was translated using a reverse independent translation procedure. The questionnaire demonstrated acceptable internal consistency, with Cronbach’s alpha coefficients ranging from 0.66 to 0.92, and a median value of 0.83. All subscales were found to be adequate.

References

Author: I. Ajzen (1985)
Greek adaptation: Theodorakis (1994)
Ajzen, I. (1991). The theory of planned behavior. Organizational Behavior and Human Decision Processes, 50(2), 179–211.
Tags: Questionnaire