When implicit promises override explicit promises: The effectiveness of guarantees and diagnostic kits in improving product evaluations

Purpose: The current research aims to explore the differential effects of bundling products with guarantees (explicit promises of product performance) or with diagnostic kits (kits that allow the user to measure actual product performance) on pre-purchase product evaluations. It is proposed that when product performance evaluation relies on external sources of information, the effect of a guarantee exceeds the effect of a self-diagnostic kit. However, when product performance evaluation relies on internal information or self-reports, product evaluations are better leveraged by an offer of a diagnostic kit than by a guarantee. Design/methodology/approach: The first study examines the differential effects of guarantees and of diagnostic kits on pre-purchase evaluations of hypothetical products as a function of the mode of evaluation of product performance (internal versus external information sources). The second study explores these effects on pre-purchase evaluations of actual products, and further includes a control condition. Findings: The findings confirm the hypothesis that a guarantee (diagnostic kit) leads to higher product evaluations than a diagnostic kit (guarantee) when product performance evaluation relies on external (internal) sources of information. Originality/value: The relative benefits of bundling guarantees or diagnostic kits to product offers have not been examined to date. The current research not only demonstrates this relative effect and its underlying mechanism, but also identifies the product attributes that contribute to this effect.