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Home arrow Engineering arrow Measuring Electronic Word-of-Mouth Effectiveness: Developing and Applying the eWOM Trust Scale

Discussion, Implications and Future Research

Summary of Research

Regardless of the insights of the majority of formal academic disciplines which have already acknowledged the key role that trust plays in the context of interpersonal communication as well as influence, research in the field of online consumer research put little emphasis on a systematic investigation of the trust concept in the context of inter-consumer communication. This situation may be not attributable to the fact that online scholars haven’t recognized the construct’s general importance also in their own research area, but is explainable by a latent conceptual confusion of what trust in eWOM really is. A variety of industry reports and academic studies have nevertheless attempted to measure the construct or closely related concepts (e.g., Briggs et al., 2002; Pan & Chiou, 2011; Racherla et al., 2012; Sen, 2007; Smith et al., 2005). While this research stream represents a valuable contribution, especially to the recognition of the important role of the trust concept for review research, these writings are commonly characterized by a lack of understanding of the construct’s content and scope. Besides these shortcomings in conceptualizing the focal construct, methodological problems in deriving adequate measurement instruments limit application of existing self-reporting scales in further research. To the best of the author’s knowledge, no measure was developed which meets the standards and requirements of contemporary scale development literature until today. In fact, online research fails by still using single-item measures or ad-hoc multiple item scales that have not been evaluated in terms of their reliability and validity. The lack of an adequate measure for a key concept of eWOM impact leads to confinements in the quality of scientific research and the limited acceptance of the discipline’s insights by the academic community, as well as practitioners. Most of all, a new measure would provide meaningful insights into the role of trust as one of the most important critical mental mechanisms that facilitates online interaction among consumers and ensures that the function of OCR as a valuable third-party evaluation mechanism is maintained.

© Springer Fachmedien Wiesbaden 2017

W. Weitzl, Measuring Electronic Word-of-Mouth Effectiveness,

DOI 10.1007/978-3-658-15889-7_6

Given this state of affairs, this thesis intends to overcome these serious restrictions by introducing a framework that is able to theoretically describe the construct of consumer generalized trust in information conveyed in online customer reviews and recommendations, developing an instrument of measuring it, and applying the new measure for investigating the construct’s role in eWOM influence among clusters of consumers. The particular objectives of the research are: (1) to clarify and advance the theoretical conceptualization of eWOM trust by investigating the construct’s conceptual meaning, as well as scope, and to provide evidence on the conceptual uniqueness of the construct which discriminates it from related but diverging eWOM concepts; (2) to introduce a reliable, generalizable, valid and practicable multi-item scale (eWT-S) that quantitatively captures trust in eWOM and is the result of a rigid measurement development process; (3) to investigate the role of eWOM trust in an e- commerce/trust framework by evaluating the concept’s antecedents, correlates, as well as consequences; and (4) to apply the new scale to segment online consumers in accordance with their generalized trust in C2C (eWOMTrust), as well as B2C communication (oADTrust), and profile the identified segments in terms of attitudinal, perceptual and habitual characteristics.

To meet the aforementioned objectives, this thesis adhered to the given standards for the accomplishment of the research process advanced by acknowledged scholars (Churchill, 1979; DeVellis, 2012; Netemeyer et al., 2003) and cherished, approved research techniques. The research process was characterized by a multi-stage/multi-sample design and was itself guided by a series of 13 research questions, as well as 15 hypotheses which all targeted the further assessment of the psychometric properties and applicability of the new measurement scale.

The first research question (RQ1) intended to evaluate the degree to which the eWOM trust construct can be understood as a complex, higher-order construct that is best described in terms of several facets. Further, this question also emphasized the investigation of the true nature of the focal construct, as it wanted to clarify that the theorized ingredients of eWOM trust are also mirrored by the empirical reality. Based on a careful review of research results from various intellectual disciplines, as well as the insights gained from the qualitative and quantitative stages of the research process, this thesis was able to globally describe eWOM trust as a consumer’s general confidence that the information conveyed in electronic word-of-mouth (eWOM) is reliable. In the context of this research, eWOM is equated and limited to online customer reviews and recommendations which are understood as peer-generated, text-based evaluations of market offerings posted on company or third-party websites by former, actual, or potential customers (Hennig-Thurau et al., 2004; Mudambi & Schuff, 2010).

This said, eWOM trust in this research is formally and more specifically defined as the extent to which a consumer believes that information given in online customer reviews and recommendations is (a) useful, (b) honest, and (c) benevolent; (d) is willing to rely on or use online customer reviews in general; and (e) is willing to depend on this kind of market information. As this thesis defines eWOM trust as a person’s generalized disposition toward relying on online customer reviews and recommendations, the focal construct is regarded as a relatively stable, trait-like attitudinal concept that predisposes individuals to react to this kind of information with internal perceptions as well as attitudes, but also determines the way consumers react in terms of their behaviour. Accordingly, eWOM trust is conceptualized here as an element of the human personality that triggers a consistent response tendency that can be observed across a wide range of situations.

Further, this definition mirrors the understanding of eWOM trust as a psychological construct, being best measured as a second-order construct that itself is reflected by five distinct types of trust - each of these five dimensions belong to one of the three underlying general trust elements (i.e., cognitive, affective, or behavioural). Hence, the conceptualization is consistent with the classic three-component view of attitude (Hogg & Vaughan, 2011). This research further concluded that on the first-order level, eWOM trust is most appropriately assessed by five separate sub-dimensions: (1) (eWOM) ability (usefulness), (2) (eWOM) integrity/honesty, (3) (eWOM) benevolence, (4) willingness to rely (use), and (5) willingness to depend (risk). eWOM trust is therefore conceptualized as a psychological collective of these five factors of trust, which themselves represent relatively stable confident beliefs in review information, as well as behavioural intentions to use and rely on online reviews under conditions of uncertainty, risk, and interdependence that are typical for this kind of interpersonal communication.

After rigid scale item purification and cross-validations, the thesis proposes a set of 22 observable indicators which seem to best capture the content and scope of the five eWOM trust dimensions. Table 53 reports the final scale items for the English and German eWT-S.



The information given in online customer reviews is ...

Informationen in Online Kundenrezensionen sind ...

Ability (eWOM Usefulness)


hilfreich (Ab7) instructive

aufschlussreich (Ab8)


nutzlich (Ab9)

applicable brauchbar (Ab10)


informativ (Ab11)

Integrity/Honesty (eWOM Reliability)

genuine echt (In2)

honest ehrlich (In3)


wahr (In4)


glaubwurdig (In5)


verlasslich (In6)

serious serios (In9)

correct richtig (In10)

eWOM Benevolence


fursorglich (Be1)

social* sozial (Be2)


gutherzig (Be3)

Willingness to rely on (use)

When I want to purchase a specific product/service, I am willing to visit online customer reviews to get relevant information.

Wenn ich ein bestimmtes Produkt/eine bestimmte Dienstleistung kaufen bin ich bereit, Online Kundenrezensionen zu bes um relevante Informationen erhalten. (Wi1)

If I want to know more about the experiences of other customers with a product/service/vendor, I am willing to look at online customer reviews.

Im Fall, dass ich mehr uber die Erfahrungen anderer Konsumenten mit einem Produkt/einer Dienstleistung/einem Handler erfahren mochte, bin ich bereit, Online Kundenrezensionen zu besuchen. (Wi4)

I am prepared to consult online customer reviews in order to find out more about the attributes of a product/service/vendor.

Ich bin bereit, Online Kundenrezensionen heranzuziehen, wenn ich mehr uber die Eigenschaften eines Produktes/einer Dienstleistung/eines Handlers erfahren mochte. (Wi5)

I would use online customer reviews to find out more about a product/service/vendor.

Ich wurde Online Kundenrezensionen verwenden, um mehr uber ein Produkt/eine Dienstleistung/einen Handler herauszufinden. (Wi8)

Willingness to depend on (risk)

I’m willing to recommend products/services/vendors which have been recommended in online customer reviews to my friends and family.

Ich bin bereit, Produkte/Dienstleistungen/Handler, die in Online Kundenrezensionen empfohlen wurden, meinen Freunden oder Familienmitgliedern weiterzuempfehlen. (Wi2)

I am willing to make relevant purchasing decisions based on online customer reviews.

Ich bin bereit, wichtige Kaufentscheidungen aufgrund von Online Kundenrezensionen zu treffen. (Wi6)

When I make purchasing decisions, I am willing to rely on online customer reviews.

Wenn ich Kaufentscheidungen treffe, bin ich bereit, mich auf Online Kundenrezensionen zu verlassen. (Wi7)

A series of research questions aided the evaluation of the final scale’s properties in terms of its reliability, as well as validity. To assess the degree of concurrent validity, the second research question (RQ2) addressed the capability of the scale to discriminate among groups of consumers that indicated varying levels of trust in online customer reviews and recommendations on an alternative, single measure of eWOM trust. For the validity assessment, consumers’ scores on the new eWOM trust scale of two consumer groupings were contrasted. The first group (high eWOM trusters) demonstrated a high level of trust on the single-item measure, while the second group (low eWOM trusters) showed a low level of trust by using the same single-item measure. Further analysis indicated that, by using the new measure, the mean within the high eWOM truster group was significantly above, compared to the average score of the low truster group. This result provided evidence that the new eWOM trust scale possesses concurrent validity.

Convergent validity targets the extent to which a new measure corresponds with alternative measurement approaches of the same construct. The third research question (RQ3) assessed this issue by comparing the eWOM trust scale with four different measures: (1) a non-diagnostic single item measure, (2) a Likert, multi-item measure of overall eWOM trust, (3) a semantic differential, multi-item measure of overall eWOM trust, and (4) a qualitative measure of overall eWOM trust. The empirical results derived from two independent samples showed significant and strong correlations, demonstrating that the alternative measures are very likely to assess one and the same construct. This supported convergent validity.

The multi-part research question four (RQ4a-d) intended to find a proof for the scale’s discriminant validity. In respect to research questions 4a and 4b, eWOM trust was theorized to differ from eWOM credibility (R&ed), as well as consumer attitude towards eWOM in general (RAtt) - two concepts which seem to be closely related but also conceptually different from the focal construct. In the course of the research, the relationship between these three constructs was subject to an empirical examination by using different methods. On the global level, the constructs’ interrelation was tested particularly by the analysis of the correlation matrix, by reviewing a Multi-trait Multi-method matrix (MTMM), as well as by comparing alternative measurement models with confirmatory factor analysis. For the MTMM, consumer responses for the three constructs were included in the form of two alternative scale formats: (a) Likert- format scale and (b) semantic differential scale. Analysis provided additional evidence for the convergent validity of the new scale, as well as strong support for its discriminant validity. The latter finding was also supported by confirmatory factor analysis, which also demonstrated that the measure of eWOM trust is distinct from the measures intended to assess consumer general attitude towards online reviews, as well as perceived online review credibility. Further analysis also included an assessment of the relationships between the individual eWOM trust subdimensions and the other two constructs. Taken together, the analyses indicated that the eWOM trust scale is related to eWOM attitude, as well as eWOM credibility, but more importantly awards the new scale properties that cannot be attributed to the alternative constructs. This research was able to show that the eWOM trust scale has some overlap with the measure of eWOM credibility, as its dimension of integrity/honesty is conceptualized very similarly. In addition, it is also agreed that the focal construct is not completely conceptually independent from eWOM attitude, as some dimensions demonstrated meaningful inter-correlations. However, the definition of eWOM trust advanced in this research also includes other facets that are regularly not found in measurement approaches of the two alternative constructs; that is, benevolence, willingness to rely (use), and willingness to depend.

Research question 4c and 4d strived for answers that should provide evidence that consumers develop trust in online reviews that is different from their personal disposition to trust others and is specific to the kind of trusting object discussed in this thesis. By means of confirmatory as well as exploratory factor analysis, it was shown that consumers typically differ in their internal tendency to put trust in generalized others and online reviewers. However, there exists a significant relationship between these separated constructs, as more disposition to trust leads, as expected, to increased levels of trust in eWOM. In addition, by measuring the level of trust in different forms of market information (e.g., traditional word-of-mouth, information from salespersons, advertising), this thesis was also able to demonstrate that consumers develop trust that is specific to different kinds of market communication and the development of mental attitudes takes place independently for the most part. Considered together, the results empirically demonstrate the construct’s distinctiveness from related eWOM, as well as personal characteristics constructs supporting the scale’s discriminant validity. This insight should alert scientists as well as practitioners to carefully distinguish between the constructs when including them in their survey research.

Another indicator of the scale’s quality is its known group validity (RQ5), which is the extent to which a measure differs as predicted between groups which should score low and high on a trait. Earlier contributions in communications research provided the necessary theoretical ground for the assumption that faculty members share characteristics (e.g., intelligence, education, age) that negatively impact this group’s general trust level in customer reviews and therefore separates them from university students that were hypothesized to score higher on the trait. As expected, the faculty sample showed an average eWOM trust level that was significantly lower than for the student sample, thus supporting known group validity.

The scale’s predictive as well as postdictive validity was addressed in research question six (RQ6). While predictive validity can be defined as the measure’s ability to effectively predict a temporally later-occurring criterion, postdictive validity in contrast assesses the new scale’s capability to predict a temporally earlier-occurring criterion. In the context of this research, this criterion was referred to as future/earlier trusting behaviours (e.g., opinion seeking, adoption, and giving). This was theoretically grounded on well-established research insights which have demonstrated close relationships between an individual’s trust and subsequent trusting or risktaking behaviours. By using a sequential study design and data from multiple samples, this thesis was able to find significant as well as reasonable linkages between these constructs. The empirical results therefore provide evidence for the existence of predictive as well as postdictive validity.

In order to test the nomological validity of the eWOM trust scale, fifteen hypothesized relationships (H1-H15) between eWOM trust and a variety of theorized antecedents, correlates, and response variables were assessed. Amongst others, it was hypothesized that the eWOM trust construct is positively and significantly related with (a) eWOM involvement, (b) eWOM usage, (c), perceived reviewer credibility, (d) perceived tie strength, (e) perceived reviewer homophily, and (f) risk propensity. On the other hand, the construct was theorized to be negatively related with (g) reviewer distrust, (h) eWOM avoidance, and (i) eWOM scepticism. The majority of the defined relationships (13 out of 15) found empirical proof, as they showed significant correlations as expected. Consequently, the eWOM trust scale was demonstrated to have nomological validity. However, this research was not able to empirically demonstrate a negative relationship of the focal construct with perceived reviewer egotism. This may be explainable by the failure to capture negative attitudes towards eWOM sources by the measurement instrument. Respondents may not like to express negative feelings or aversions in respect to others. Additionally, the relationship between eWOM trust and consumer selfconfidence turned out to be significant but in the opposite direction to that theorized (for a possible explanation see below).

As this research proposes a new scale that is applicable to paper-based as well as online questionnaires, answers from respondents are not immune to common problems, such as the adulteration by a social desirability bias. This research tested the scale by correlating it with the Crowne-Marlowe social desirability scale. As this correlation was shown to be weak and insignificant, it was concluded that the new scale is not seriously imperilled by socially desirable responding.

The remaining research questions targeted supplemental reliability, as well as generalizability assessments, which also included an evaluation of the scale’s test-retest reliability (RQ7). Here, the main emphasis lies on the investigation of the measure’s temporal stability across a series of sequenced surveys. By using data from a sample of 50 respondents and the administration of the new scale in two survey occasions three weeks apart, this research was able to demonstrate significant correlations between the two responses. This supported test-retest reliability, as the new scale seemed to be capable of robustly measuring a personal characteristic across time.

Research question eight (RQ8) asked whether the eWOM trust scale could be generalized to validly measure consumer trust in online reviews on different eWOM platforms. Two types of online platforms were considered: consumer- (CDS) and marketer-driven (MDS) eWOM sites.


By applying confirmatory factor analysis, reasonable support for the WOM trust scale with the original factor structure was gained for both contexts. Besides adequate characteristics in respect to the scale’s convergent as well as discriminant validity, it also showed desirable reliability properties, indicating that the scale is able to adequately assess trust in reviews on consumer- (e.g., online discussion forums) as well as marketer-developed (e.g., merchant websites) review sites. Consumers showed similar trust in both types of sites. This finding is in contrast with other research (e.g., Bray & Schetzina, 2006). However, this study maybe was not able to find differences as the respondents were prompted to think about the two categories in general and not specific examples. Additional evidence for the scale’s validity was provided by investigating the relationships between platform-specific eWOM trust and platform’s eWOM credibility (RQ9a), as well as perceived credibility of reviewers on these two platforms (RQ9b), which are both theorized to represent correlates/antecedents of the focal construct. Empirical evidence mirrors a reasonably strong and significant relationship between the constructs. Hence, this study led to the acceptance of the scale’s ability to generalize over different platform contexts.

This research has conceptualized eWOM trust as a personal characteristic of the consumer that predisposes the individual to rely on online customer reviews and recommendations. In its function therefore, the construct is assumed not to perfectly predict his/her response to every individual review but explain to some degree behavioural and attitudinal tendencies towards specific reviews. Accordingly, research questions 10 and 11 both targeted this issue by striving for evidence for a positive relationship between generalized eWOM trust and trust in (RQ10) and attitude towards individual reviews (RQ11). In the course of an empirical investigation, respondents were first asked to indicate their personal level of eWOM trust in the new scale before later evaluating different sets of online reviews for four alternative products (brands). The results showed - as assumed - that eWOM trust can be regarded as a good predictor of individual review perception and/or attitude.

The fact that the eWOM trust scale was developed in German - by using empirical data from Austrian as well as German respondents - may limit its application to this cultural and language context. In order to overcome this restriction, this thesis intended to demonstrate the robustness of the scale by distributing an English version to a sample of US online customers and to test its psychometric properties (RQ12). By means of exploratory as well as confirmatory factor analysis, this research was able to provide initial evidence for the scale’s invariance across different languages and countries. All but a single item (i.e., “social”) were demonstrated to be integral elements of the adopted scale showing adequate psychometric properties. The same was also true for the proposed overall measurement model, which gives confidence that the proposed eWOM trust scale is likely to capture the nature and the occurrence of the construct among consumers, independent of the language context of its application. The fresh sample of US respondents also aided the establishment of multi-sample scale norms and the demonstration of differences in the level of trust among consumer groupings (i.e., Americans placed more trust in eWOM than Germans/Austrians), which may be attributable to the cultural and social background.

The last research question (RQ13) emphasized the new scale’s contribution to meaningfully segmenting online consumers. Here, the thesis at hand investigated a typology based on trust in online customer reviews (eWOMTmst) and trust in online advertising (oADTrust) as independent dimensions. The implication of this examination is that contemporary consumers typically have access to two major forms of online market communication - that is, online customer reviews (eWOM) as consumer-to-consumer information and online advertising (Online Ads) as business-to-consumer information. As consumers develop trust that is specific to these communication forms - making them more or less amenable to their contents and specific claims - both orientations need to be included in order to form groups that vary in respect to their persuasibility by marketer-driven vs. public-driven communication. The cluster analysis resulted in a four-segment solution. Pure ad trusters, who solely rely on information provided by companies, were not found in the sample. Instead, a segment with high trust in online reviews and non-existing trust in online advertisements was uncovered (Pure review trusters, 19% of respondents). The remaining three segments were characterized by an increasing amount of eWOM, as well as ad, trust. For instance, Low trusters (10%) formed a segment within which trust in both forms was not existing. In contrast, a third (Moderately trusting consumers, 41%) and a fourth segment (High trusters, 30%) were identified, suggesting that a large proportion of consumers are relatively open to information given online and are likely to integrate it in their purchase decision; however, trust in the opinions and recommendations of fellow shoppers was significantly higher compared to its marketer-driven counterpart (in every cluster).

The variety of research questions and selection of hypotheses enabled this research to conduct a rigid scale development process that included a series of demanding tests for the scale’s reliability, validity, generalizability, practicability, as well as cross-national stability. These tests conjointly provided evidence for the psychometric soundness of the scale. Therefore, the eWOM trust scale provides a parsimonious, reliable, and valid measurement instrument which could be used both for scientific theory testing endeavours, just as well as for practical identification of eWOM trusting consumers.

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