Predictive Validity of Evidence-Based Persuasion Principles: An Application of the Index Method

Purpose – This paper aims to test whether a structured application of persuasion principles might help improve advertising decisions. Evidence-based principles are currently used to improve decisions in other complex situations, such as those faced in engineering and medicine. Design/methodology/approach – Scores were calculated from the ratings of 17 self-trained novices who rated 96 matched pairs of print advertisements for adherence to evidence-based persuasion principles. Predictions from traditional methods – 10,809 unaided judgments from novices and 2,764 judgments from people with some expertise in advertising and 288 copy-testing predictions – provided benchmarks. Findings – A higher adherence-to-principles-score correctly predicted the more effective advertisement for 75 per cent of the pairs. Copy testing was correct for 59 per cent, and expert judgment was correct for 55 per cent. Guessing would provide 50 per cent accurate predictions. Combining judgmental predictions led to substantial improv...