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To qualify for inclusion, studies must have specifically evaluated celebrity characteristics. Advertising studies that examined source effects without specifically addressing celebrities or provided an evaluation of celebrities in comparison to other types of spokespersons were too general for inclusion. Eighty-seven studies were originally identified as worthy of further evaluation. Of this sample, 12 articles were conceptual and another 43 studies failed to report information required to conduct the analysis due to their focus on aspects of celebrity endorsers outside the realm of source effects. In total, then, 32 studies were retained for analysis in this meta-analysis. Total effect size was 266. In all, 27 journal articles, two unpublished studies, and three unpublished dissertations were included.

While an extensive search was conducted, the articles included in this meta-analysis probably represent a sample, as opposed to the complete population, of the celebrity endorsement literature. But given the wide diversity of journals as well as the unpublished works (See Table 1) contained in the sample, it should be representative of the relevant advertising literature.

Table 1: Journal articles collected for meta-analysis

Coding Data

Correlations were obtained from the sample studies using formulas from Cooper and Hedges (1994). As suggested by Hunter and Schmidt (1990), weighted correlations were used in the analysis to account for sample size and also as the dependent variable in the analysis. For the independent variables, initial coding consisted of coding the independent variables exactly as the authors articulated them. These independent variables were then reinterpreted and grouped into redefined variables.

These redefined variables were then presented to five experts in the area of advertising for confirmation. A content analysis of the studies yielded six substantive and methodologically meaningful dimensions on which all studies could be compared. The dimensions were source manipulation, celebrity/product fit, experimental effect, study setting, sample type, and origin. Coding was performed by two trained coders. Any disagreements about potential inconsistencies in the coding were resolved through discussions involving the authors and consulting experts.

ANALYSIS

Table 2 summarises the effects from the sample studies. Among the original 266 total effects, 185 were statistically significant (p < 0.05). Forty-four per cent of the retained studies examined celebrity/product fit. With respect to methods characteristics, 86% of studies sampled reported main effects, 62% used a survey instrument, and 52% used a student sample. Exactly 60% of the studies used a US-based sample.