Tipping the Scale: The Role of Discriminability in Conjoint Analysis

Research Scale expansion influences consumers' choices. Choice-based conjoint is a widely used method that infers importance of product attributes by observing choices. Previous research had not examined the impact of scale expansion onmetrics derive from conjoint analysis. We hypothesize that scale expansion would initially increase consumers' ability to discriminate between alternatives, making them more likely to choose alternatives that are superior on expanded attributes, then decrease it due to diminishing sensitivity, impacting derived relative importance and screening propensity. Methods In three choice-based (one incentive compatible) conjoint studies with over 1,700 participants recruited from both a nationwide online panel and a university, we demonstrate the impact of attribute representation in their choices among cars and snack bars. Findings We demonstrate the impact of attribute representation in choices. Specifically, we observe an inverted-u pattern for inferred relative importance derived from partworths, measures of perceived differences in attribute values, and screening propensity in response to scale expansion. This is important for academics or practitioners employing the conjoint method to appreciate because both consumer choice and their own inferences will depend on the specific scale expansion utilized. Implications Representation of important product attributes are changing (e.g., fuel usage on the Monroney sticker, recent mandate to change serving size information). Because choice depends on scale expansion, consumers should recognize this bias while policy makers can consider implementing the most socially beneficial levels. Practitioners should appreciate that their scale's expansion will determine their conjoint results. By illustrating the curvilinear relationship between scale expansion and multiple measures, we offer policy makers and practitioners some insight into the limits of scale expansion.