Ads promoting OTC medications: The effect of ad format and credibility on beliefs, attitudes, and purchase intentions

This investigation explores the effects of ad credibility and ad format (direct comparative vs. noncomparative) on consumers' beliefs, attitudes, and purchase intentions for over-the-counter (OTC) medications. It is hypothesized that ad credibility moderates the effects of ad format. To test the hypotheses three different experiments were conducted, with each one using a different method to manipulate ad credibility (multiple explanations for claimed superiority, claim substantiation, and approval of ad information from the Federal Trade Commission). The results of the three studies provide consistent support for the main effects of ad credibility and ad format. Increased persuasion was evidenced with higher credibility ads and with direct comparative ads. However, the hypothesized interaction consistently was not supported. Implications of these findings are discussed. (C) 1997 Elsevier Science Inc.