Methodology
We keep seven independent concepts separate and never merge them into one number: offer eligibility, current price, total known cost, historical price position, evidence confidence, purchase recommendation, and affiliate-link validation.
Immutable price observations
Every price observation is stored as an immutable record in integer minor units with a UTC timestamp. We never update prices in place; a new observation is a new row. Unknown shipping or fees are never treated as zero.
Total known cost
We compute item price, shipping, fees and a verified coupon separately. We only claim a "lowest total" when comparable, complete totals exist. A conditional coupon is not subtracted from the total, and membership-only prices are clearly labelled.
Evidence confidence (deal-confidence-v1)
A 0–100 score built from five weighted components. Hard gates override the numeric score entirely when minimum evidence is missing — we then show "insufficient data" rather than a misleading number.
version: deal-confidence-v1 · HIGH ≥ 80 · MODERATE ≥ 60
- Freshness: 25
- History depth & coverage: 25
- Independent retailer breadth: 20
- Match certainty: 15
- Total-cost completeness: 15
min history: 10 observations · 7 distinct days · freshness ≤ 14d
Price position
Position describes where the current price sits within the same variant’s own history (historical-low / low / typical / high). It is a historical assessment, not a prediction.
Purchase recommendation
States: buy now, consider, wait, insufficient data — all derived from explicit, documented thresholds. "Wait" means the price has typically been lower; it is not a forecast. We never make a market-wide recommendation from a single retailer.
Affiliate links & privacy
We record click intent with minimal data and without delaying navigation, and we never store the raw affiliate URL, tracking tag, IP address or user identity. A click never determines whether navigation succeeds.
As an Amazon Associate, Qarn360 earns from qualifying purchases.