The paper provides another example of how the Index method can provide more accurate forecasts than alternative evidence-based methods for problems where many variables are known to be relevant. (Index models were tested for forecasting political elections in earlier research, and met with considerable success.)

The PPI correctly predicted which of a pairs of advertisements was more effective for 74 percent of forecasts for 97 pairs. The usual current method for picking which ad to run, expert judgment was—with 55 percent correct—little better than chance.

The paper, titled "Predictive validity of evidence-based persuasion principles: an application of the index method," is published in the European Journal of Marketing, here. Further analysis of the predicitive validity of the Index method—in the form of a PPIx model that uses theoretical rather than empirical weights—is described in Green, Armstrong, Du, and Graefe's paper "Persuasion Principles Index: ready for pretesting advertisements", here.

Advertisers and others responsible for persuasive messages can use the Persuasion Principles Index (PPI) to predict the effectiveness of alternative implementations of their message by using the software available from the Advertising Principles site, Readers who are interested in previous evidence on the predictive validity of the Index method can find it on the index model pages of the site.