Electronic word of mouth (eWOM) highly influences costumers. Main questions of this study: Are total ratings (= social proof) more powerful than personal ratings (= direct experience)? Can a powerful brand buffer the effect of the ratings? Two kinds of eWOM are compared regarding positive and negative effects.

1. Prof. Dr. C. Bosau, RFH Köln
Levi Meyer, RFH Köln
Believing in social proof or personal experience? -
Contrasting and comparing the effect of different kinds
of eWOM in online shops
Contact: christian.bosau@rfh-koeln.de
General Online Research Conference
GOR 19
6-8 March 2019, TH Köln University of Applied
Sciences, Cologne, Germany
This work is licensed under a Creative Commons Attribution 4.0 International License (
http://creativecommons.org/licenses/by/4.0/)
Suggested citation: Bosau, C. & Meyer, L. 2017. “Believing in social proof or personal experience? - Contrasting and
comparing the effect of different kinds of eWOM in online shops” General Online Research (GOR) Conference, Cologne.

2. Believing in social proof or personal
experience?
Contrasting and comparing the effect of
different kinds of eWOM in online shops
C. Bosau & L. Meyer

3. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience?
Let‘s buy a speaker ...
3

4. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience?
Former results
4
What we already know:
• Improvement in reviews leads to an increase in sales – here: for books (Chevalier &
Mayzlin, 2006)
• Favorable reviews increase sales – though the reviewer quality, the reviewer
exposure, the product coverage as well as the age of the product play an
important role (Hu, Liu & Zhang, 2008)
• The more negative online consumer reviews the worse the product attitude gets
– especially with high-quality negative reviews and especially for high involved
costumers (Lee, Park & Han, 2007)
• Low numerical ratings are trusted - regardless of the number of ratings - more
than high ratings. High ratings are only trustworthy if there is a high number of
ratings (Gavilan, Avello & Martinez-Navaroo, 2018)

5. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience?
Former results
5
What we already know:
• A „prototypic“ single customer review does have a stronger effect on product
attitudes than aggregated review scores. (Ziegele & Weber, 2015)
• Customers are highly influenced by single affect-rich reviews, i.e. more
influenced by this anecdotal information than by statistical information like overall
ratings (van Helversen, Abramczuk, Kopec & Nielek, 2018)
• Likewise: single customer reviews that do not include many diverse arguments
do not seem to have much persuasive power (Hong & Park, 2012)
Main questions:
• Are total ratings (= social proof) more powerful than personal ratings
(= direct experience)?
• Are there differences for branded vs. no-name-products?

6. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience?
The new study
6
Former studies:
§ looked at the outcomes and
the effects of online ratings
This study:
§ contrasted two kinds of eWOM (total vs.
personal ratings)
§ compared the effect of positive vs.
negative ratings
§ analyzed the potential buffering effect of
brand power
§ looked at technical products
Method study:
• Online questionnaire (posted via Facebook, mailing-lists and personal emails,
partly snowball sampling) in 2018; N = 166
• 2 x 2 x 2 experimental research design
• age: < 20y = 5%, 20-29y = 65%, 30-39y = 5%, 40-49y = 10%, > 49y = 15%
• male = 34%, female = 66%

7. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience?
The hypotheses
7
Main effects:
• brand products will be rated higher than no-name-products
• positive total ratings will lead to better decision outcomes than negative total ratings
• positive personal experience will lead to better decision outcomes than negative personal
expierence
customer decision
(quality, buying &
recommendation)
Brand effect
Total rating
personal experience
Interaction effects:
• the effect of ratings is smaller for branded than for no-name-products (brand
buffering effect)
• THOUGH: positive rated no-name-products might score higher than negatively
rated brand products

8. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience?
The research design
2 x 2 x 2 design:
Personal experience
(repeated mesurement)
posi.ve experience nega.ve experience
Brand ( N= 85) vs.
No-name-product (N = 81)
Brand ( N= 85) vs.
No-name-product (N = 81)
Brand No-Name Brand No-Name
Total ra.ng
(repeated
measurement)
posi.ve
ra.ng
1 2
Example
(next slide) 4
nega.ve
ra.ng
5
Example
(next slide) 7 8
each person rated 4
scenarios: e.g. number 1,
3, 5, 7
no repeated
measurement for the
brand factor

9. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience?
The decision scenarios
9
Example: Brand product, GOOD total
rating, BAD personal expierence
Example: No-name-product, BAD total
rating, GOOD personal expierence
experimentally
manipulated
experimentally
manipulated

10. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience?
The dependent variables
product quality buying intention
recommendation to
friends
THOUGH: High intercorrela.on between the 3
indicators à summarized to one single measure
„customer decision“

11. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience?
The results – main effects
11
2,56 2,32
0
1
2
3
4
5
Brand No-name
Brand vs. No-name
3,11
1,77
0
1
2
3
4
5
posi.ve nega.ve
Total ra2ng
3,14
1,73
0
1
2
3
4
5
posi.ve nega.ve
Personal experience
ü Small effect of
Brand/No-Name:
F(1)=4.43, p < .05, part. η2 = .03
ü Big effect of
Total rating:
F(1)=161,17, p < .00, part. η2 = .50
ü Big effect of
Personal experience:
F(1)=181.26, p < .00, part. η2 = .53
v Brand products are rated – interestingly – only slightly higher than no-name-
products.
v Positive ratings increase strongly – as expected – the customer decision.
Personal experience had a slightly higher effect than the total rating.

12. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience?
The results – interaction effects
12
ü Small interaction effect of
total rating & personal experience:
F(1)=9.80, p < .01, part. η2 = .06
The results of the combination of
total rating and personal experience:
v the customer decision is
especially improved if both ratings
are positive
v negative total rating (together with
positive personal experience)
have the same effect compared to
positive total rating (together with
negative personal experience)
3,91
2,38
2,32
1,15
0
1
2
3
4
5
posi.ve nega.ve
posi.ve
nega.ve
total rating
personal
experience

13. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience?
The results – interaction effects
13
ü Small interaction effect of
total rating & personal experience & brand:
F(1)=4,27, p < .05, part. η2 = .03
3,73
2,26
2,31
0,96
0
1
2
3
4
5
posi.ve nega.ve
No-name products
posi.ve
nega.ve
total rating
personal
experience
4,09
2,5
2,32
1,34
0
1
2
3
4
5
posi.ve nega.ve
Brand products
posi.ve
nega.ve
total rating
personal
experience
v Only a small buffering effect can be found for brand products:
the customer decision is not as bad as expected if both – the total rating &
the personal experience – are negative.

14. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience?
The results – interaction effects
v Only a small buffering effect can be found for brand products:
the customer decision is not as bad as expected if both – the total rating &
the personal experience – are negative.
Brand vs.
No-name
Total ra2ng
Personal
experience
Customer
total
decision
Brand posi.ve posi.ve 4,09
No-Name posi.ve posi.ve 3,73
Brand nega.ve posi.ve 2,50
Brand posi.ve nega.ve 2,32
No-name posi.ve nega.ve 2,31
No-name nega.ve posi.ve 2,26
Brand nega.ve nega.ve 1,34
No-name nega.ve nega.ve 0,97
x n.s.
x n.s.
ü small effect:
F(1)=5.84, p < .05, part. η2 = .03

15. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience? 15
§ Online customer reviews DO HAVE an important influence on customer decisions.
§ This study supports, that personal experience might even be more powerful than a total
rating’s score (though, the effect here was very small – maybe due to very short personal
reviews)
§ If personal reviews are very short: There is no real difference between bad total
scores and good personal reviews compared to good total scores and bad
personal reviews, i.e. having bad reviews in either of the two lead to worse
customer decisions
§ Look for both: good overall ratings as well as good personal reviews, since the
combination of both improves the customer decision most
§ Brand products are not in general immune to negative eWOM. Only if total scores as well
as personal reviews are bad, the brand buffers a bit the negative affect compared to no-
name products.
Conclusion
For marketeers:
Be careful about the total ratings as well as the personal
reviews that are generated in online stores.

16. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience? 16
• Chevalier, J. A. & Mayzlin, D. (2006). The Effect of Word of Mouth on Sales: Online Book
Reviews. Journal of Marketing Research, Vol. XLIII, pp. 345-354.
• Gavilan, D., Avello, M. & Martinez-Navaro, G. (2018). The influence of online ratings and
reviews on hotel booking consideration. Tourism Management, Vol. 66, pp. 53-61.
• Hong, S., Park, H.S. (2012). Computer-mediated persuasion in online reviews: Statistical
versus narrative evidence. Computers in Human Behavior, Vol. 28, pp. 906–919.
• Hu, N., Liu, L. & Zhang, J. J. (2008). Do online reviews affect product sales? The role of
reviewer chracteristics and temporal effects. Inf Technol Manage, Vol. 9, pp. 201-214.
• Lee, J., Park, D. H. & Han, I. (2008). The effect of negative online consumer reviews on
product attitude: An information processing view. Electronic Commerce Research and
Application, Vol. 7, pp. 341-352.
• van Helversen, B., Abramczuk, K., Kopec, W. & Nielek, R. (2018). Influence of consumer
reviews on online purchasing decisions in older and T younger adults. Decision Support
Systems, Vol. 113, pp. 1-10.
• Ziegele, M. & Weber, M. (2015). Example, please! Comparing the effects of single customer
reviews and aggregate review scores on online shoppers’ product evaluations. Journal of
consumer behaviour, Vol. 14, pp. 103-114.
Literature

17. GOR 2019
Bosau & Meyer: Believing in social proof or personal experience? 17
Thank you very much for your
attention!
Contact details:
Rheinische Fachhochschule Köln
Prof. Dr. Christian Bosau, Dipl.-Psych. & Master of HRM & IR
Schaevenstraße 1a/b
50676 Köln
Tel.: +49 221 20302-0
e-mail: christian.bosau@rfh-koeln.de
Slideshare: cbosau
Twitter: cribocologne