Discrimination as default

Participants are assigned to Group X or Group Y. In Phase 1, one seller is more likely to provide good products in Group X, conditional on the product rating. In Group Y, both sellers are equally likely to provide good products. In Phases 2-4, seller identity does not predict quality in either group.

In Phase 3, Group X participants are assigned to one of five conditions:
- Routine Control: no intervention and a decision timer.
- Routine Information: participants are told that seller identity no longer predicts quality, with a decision timer.
- Routine Procedure: participants confirm the product rating before deciding, with a decision timer.
- Deliberative Information: participants receive the information intervention without a decision timer.
- Deliberative Procedure: participants complete the rating-confirmation procedure without a decision timer.

Group Y remains in the routine control condition. In Phase 4, all participants return to routine decisions without an intervention. Which seller is initially designated as the better seller is independently randomized.

2026-08-24

2026-11-30

Participant-level rating-adjusted seller gap in Phase 2.
Participant-level rating-adjusted seller gap in Phase 3.
Participant-level rating-adjusted seller gap in Phase 4.
Phase 3 differences in seller gaps across treatment arms.
Phase 3 seller gap when Phase 2 beliefs about the sellers are equal or nearly equal.
Phase 3 crossover effect between intervention type and decision environment.

The experiment has four phases. Phase 1 contains 50 decisions, Phase 2 contains 10 decisions, Phase 3 contains 15 decisions, and Phase 4 contains 10 decisions.

Five arms belong to Group X and experience a Phase 1 quality difference between sellers. These arms are Routine Control, Routine Information, Routine Procedure, Deliberative Information, and Deliberative Procedure. The sixth arm is Group Y, in which both sellers have equal quality throughout the experiment, and serves as the pure control group for comparison.

In Phases 2-4, both sellers follow the same quality schedule. In Phase 3, Group X participants receive their assigned intervention and decision environment. In Phase 4, all participants return to routine decisions without an intervention.

The primary Phase 3 analysis compares each Group X intervention arm with Routine Control. The main interaction test compares the relative effectiveness of Information and Procedure across routine and deliberative environments. We also examine whether seller-based purchasing persists when Phase 2 beliefs about the two sellers are equal or nearly equal.

The target sample is 1,500 participants, with 250 participants in each arm.

Not available

Randomization is performed by computer within Qualtrics. Participants are assigned with equal probability to one of six arms. The seller designated as initially better is independently randomized between Seller A and Seller B with equal probability.

The unit of randomization is the individual participant. Treatment arm and the identity of the initially better seller are both randomized at the participant level.

No

N/A

1500

250

The target sample is 1,500 participants, with 250 participants in each of six individually randomized arms. Outcomes are measured at the participant level, so no clustering adjustment is required. All calculations assume 80% power and a two-sided 5% significance level. For H5 (see PAP), the minimum detectable seller gaps are 7.8 percentage points among participants with exactly equal beliefs (SD = 23.5pp), 5.6pp among participants with near-converged beliefs (SD = 23.3pp), and 4.8pp for the continuous belief-gap specification evaluated at equal beliefs (effective SD=27.0pp). For the principal Phase 3 crossover test, the MDE is 8.9pp. This calculation uses the pilot arm-specific standard deviations (approximately 20pp, 20pp, 20pp, and 36pp) and corresponds to about 0.36 of the pooled individual-level outcome SD.