Marketing & consumer behavior
Purchase intention scale: Dodds (1991) or TPB
- Concept
- Purchase Intention
- Field
- Marketing & consumer behavior
- Scales in the library
- 3
- Items
- 10
Purchase intention is the degree to which a person is ready and plans to buy a product or service in the near future. It is the most common dependent variable in marketing and business theses, usually placed at the end of the model. The concept appears in Ajzen's theory of planned behavior (TPB), in the price, quality and value model of Dodds, Monroe and Grewal (1991), and in brand loyalty research. Common topics in Vietnam: intention to buy organic food, vegan cosmetics, products via livestream, sustainable fashion.
Comparing the scales
| Scale | Author (year) | Items | Response format | When to use it |
|---|---|---|---|---|
| Willingness to Buy (WTB) Willingness to buy scale | Dodds, Monroe & Grewal (1991) | 5 | Likert 7-point | Choose this when the study considers price, perceived quality and the decision to buy a specific product with a listed price. |
| Behavioral Intention (INT) Theory of Planned Behavior (TPB) scale | Francis et al. (2004) | 3 | Likert 7-point | Choose this when the model is based on TPB; specify the behavior and time frame, for example buying vegan cosmetics in the next 3 months. |
| Purchase Loyalty (PL) Brand trust, affect & loyalty | Chaudhuri & Holbrook (2001) | 2 | Likert 7-point | Choose this when respondents have used the brand and you want to measure repurchase intention, not first purchase. |
Items of each scale
Original English wording from the published source. Replace placeholders such as [system] or
[brand] with what your study is about, and pilot the questionnaire with 20 to 30 respondents first.
Willingness to Buy (WTB) · Willingness to buy scale
| Code | Item |
|---|---|
| WTB1 | The likelihood of purchasing this product is (very high … very low). |
| WTB2 | If I were going to buy this product, I would consider buying this model at the price shown. |
| WTB3 | At the price shown, I would consider buying the product. |
| WTB4 | The probability that I would consider buying the product is (very high … very low). |
| WTB5 | My willingness to buy the product is (very high … very low). |
Source: Dodds, Monroe & Grewal (1991). Response scale, licence and APA reference: Willingness to buy scale.
Behavioral Intention (INT) · Theory of Planned Behavior (TPB) scale
| Code | Item |
|---|---|
| INT1 | I expect to [perform the behavior]. |
| INT2 | I want to [perform the behavior]. |
| INT3 | I intend to [perform the behavior]. |
Source: Francis et al. (2004). Response scale, licence and APA reference: Theory of Planned Behavior (TPB) scale.
Purchase Loyalty (PL) · Brand trust, affect & loyalty
| Code | Item |
|---|---|
| PL1 | I will buy this brand the next time I buy [product name]. |
| PL2 | I intend to keep purchasing this brand. |
Source: Chaudhuri & Holbrook (2001). Response scale, licence and APA reference: Brand trust, affect & loyalty.
Tips
- Purchase intention should have at least 3 items for stable Cronbach's alpha and CFA; the 2-item repurchase scale of Chaudhuri and Holbrook should be supplemented with 1 self-written item, stated clearly in chapter 3.
- State the object and time frame in the question (which product, how long). Generic questions like 'I will buy' give poorly dispersed data.
- The Dodds et al. scale uses end-point pairs 'very high ... very low'. If you convert to agree-disagree Likert, reverse the order so a high score means high intention and note the adjustment.
- If respondents have never bought the product, put a screening question at the start of the questionnaire to separate first-time buyers from repeat buyers.
Once you have a scale, put the concept in the research model drawer to state your hypotheses, work out the minimum sample size, and after data collection check reliability with the Cronbach's alpha calculator.
Frequently asked questions
Should I use the Dodds or the TPB purchase intention scale?
If your model has attitude, subjective norms and perceived behavioral control, use the 3 TPB intention items for consistency. If the model revolves around price, perceived quality and perceived value, use the Dodds et al. (1991) willingness-to-buy scale.
How many items does purchase intention need?
At least 3 to assess reliability and convergent validity. The Dodds scale has 5 items and the TPB scale has 3, both meeting this requirement.
Can purchase intention be measured with a 5-point Likert scale?
Yes. Many theses convert the original 7-point scale to 5 points for easier answering. State the response scale in chapter 3 and keep the same scale for all constructs in the model if possible.