Marketing & consumer behavior
Source credibility scale (KOL): how to measure it
- Concept
- Source credibility (KOL, endorser)
- Field
- Marketing & consumer behavior
- Scales in the library
- 3
- Items
- 15
Source credibility is how audiences evaluate the person delivering a message, for example a celebrity, KOL, or KOC recommending a product. Ohanian (1990) measures the concept with 15 pairs of opposing adjectives divided among three components: attractiveness, trustworthiness, and expertise. In Vietnam, the scale is often used in theses on influencers on TikTok and YouTube, livestream selling, and their effect on brand attitude or purchase intention.
Comparing the scales
| Scale | Author (year) | Items | Response format | When to use it |
|---|---|---|---|---|
| Attractiveness (ATT) Source credibility scale | Ohanian (1990) | 5 | 7-point | Attractiveness; 5 adjective pairs. Important for beauty and fashion products. |
| Trustworthiness (TRU) Source credibility scale | Ohanian (1990) | 5 | 7-point | Trustworthiness; 5 adjective pairs. Often a strong predictor of purchase intention in KOL theses. |
| Expertise (EXP) Source credibility scale | Ohanian (1990) | 5 | 7-point | Expertise; 5 adjective pairs. Suitable when the endorser is an expert, doctor, or tech reviewer. |
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.
Attractiveness (ATT) · Source credibility scale
| Code | Item |
|---|---|
| ATT1 | Unattractive – Attractive |
| ATT2 | Not classy – Classy |
| ATT3 | Ugly – Beautiful |
| ATT4 | Plain – Elegant |
| ATT5 | Not sexy – Sexy |
Source: Ohanian (1990). Response scale, licence and APA reference: Source credibility scale.
Trustworthiness (TRU) · Source credibility scale
| Code | Item |
|---|---|
| TRU1 | Not dependable – Dependable |
| TRU2 | Dishonest – Honest |
| TRU3 | Unreliable – Reliable |
| TRU4 | Insincere – Sincere |
| TRU5 | Untrustworthy – Trustworthy |
Source: Ohanian (1990). Response scale, licence and APA reference: Source credibility scale.
Expertise (EXP) · Source credibility scale
| Code | Item |
|---|---|
| EXP1 | Not an expert – Expert |
| EXP2 | Inexperienced – Experienced |
| EXP3 | Unknowledgeable – Knowledgeable |
| EXP4 | Unqualified – Qualified |
| EXP5 | Unskilled – Skilled |
Source: Ohanian (1990). Response scale, licence and APA reference: Source credibility scale.
Tips
- Each item is a pair of adjectives answered on a bipolar scale, not an agreement Likert item. Put a lead-in such as 'In your opinion, [the endorser] is someone who is:' before the adjective pairs.
- If you convert to Likert items ('[the endorser] is attractive'), state that you adapted Ohanian (1990); do not cite it as the original.
- Show respondents a photo or clip of the specific endorser and ask a screening question about how well they know that person before they rate them.
- Attractiveness and trustworthiness sometimes cross-load in Vietnamese samples; check discriminant validity with HTMT.
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
Have studies in Vietnam used Ohanian's scale for KOLs?
Yes. Khuong An et al. (2024) used Ohanian's three components for cosmetics influencers (269 people, alpha 0.768 to 0.859), and Le, Vu and Le (2024) used it for beauty vloggers and vegan cosmetics (382 people, alpha 0.804 to 0.904); both were published in Innovative Marketing 20(3).
Can I use only one or two components?
Yes, if your literature review shows that component matters for your thesis. Then cite the correct number of items for the component and do not call it source credibility in general.
How does source credibility differ from brand trust?
Source credibility is an evaluation of the person delivering the message; brand trust is an evaluation of the brand itself. In KOL models, source credibility usually affects brand attitude and then purchase intention.
References
- Khuong An, G., Thuy An Ngo, T., Tu Tran, T., & Thy Nguyen, P. (2024). Investigating the influence of social media influencer credibility on beauty product purchase behaviors: A case study from Vietnam. Innovative Marketing, 20(3), 261–276. https://doi.org/10.21511/im.20(3).2024.21
- Le, B. N., Vu, V. T., & Le, M. T. (2024). Source credibility of beauty vloggers and consumer purchases of vegan cosmetics: The mediating role of cognitive and affective attitude. Innovative Marketing, 20(3), 14–27. https://doi.org/10.21511/im.20(3).2024.02