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METHODOLOGY

How Scoring Works

Tested at Depth weights every review by the reviewer's certification level. A score from a GUE Cave 2 diver counts multiple times more than one from a recreational diver. This page explains exactly how the math works — nothing is hidden.

Reviewer Credibility Tiers

Each diver's tier is determined by their highest qualifying certification. Tiers are displayed as a named badge — never as stars. Stars are reserved for product ratings only.

5
Tech / Cave InstructorWeight ×5

GUE Tech/Cave Instructor · TDI Trimix/Cave Instructor · IANTD equivalent instructor ratings

4
Advanced Technical DiverWeight ×4

GUE Tech 2 · GUE Cave 2 · TDI Advanced Trimix · TDI Full Cave · CCR MOD 2+ · IANTD equivalents

3
Entry Tech / Senior ProWeight ×3

GUE Tech 1 · GUE Cave 1 · CCR MOD 1 · TDI Decompression Procedures/Helitrox · OWSI with 5+ specialty instructor ratings

2
Dive ProfessionalWeight ×2

Divemaster (any agency) · OWSI with fewer than 5 specialty instructor ratings

1
Recreational DiverWeight ×1

Open Water · Advanced Open Water · Rescue Diver (any agency)

All certifications start as unverified. Unverified reviewers still get their tier and weight — but their badge has no checkmark.
Upload a photo of your cert card for manual admin verification. Verified reviewers get a checkmark (✓) on their badge.
When a reviewer upgrades their cert after posting reviews, old reviews keep their original weight. Weights are snapshotted at submission time.

Review Categories

Every review scores up to seven categories, each rated 1–5 or N/A. N/A means "I have no basis to judge this" — it is completely excluded from all calculations. It is never treated as a zero.

1
Reliability
Does it keep working dive after dive, without failure or degradation?
2
Functionality
Does it do its job well in the water, performing as advertised?
3
Build Quality
Materials, finish, robustness — does it feel like it will last?
4
Aftermarket Support
Spares availability, service network, and manufacturer responsiveness.
5
Value for Money
Performance relative to the price paid.
6
Comfort & Ergonomics
Fit, adjustment, button/control feel, comfort over long dives.
7
Travel & Packability
Weight, bulk, and ease of flying with it.

At least one category must be rated. A review cannot be all N/A.

Score Formulas

Step 1 — Review Overall

Each review's overall score is the plain average of its non-N/A category ratings.

review_overall = average of non-N/A category ratings

Example: Reliability 5 · Functionality 4 · Build Quality 4 · Aftermarket N/A → (5+4+4)÷3 = 4.33

Step 2 — Weighted Product Score

The weighted score across all reviews of a product, where each review's contribution is scaled by the reviewer's tier weight.

weighted_score = Σ(weight × review_overall) ÷ Σ(weight)

The same formula applies per-category, only including reviews where that category was rated.

Step 3 — Bayesian Adjustment

A product with one 5-star review shouldn't outrank a product with 50 reviews averaging 4.8. The adjusted score applies shrinkage toward the site-wide average to prevent outliers dominating ranking lists.

adjusted_score = (C × site_avg + Σ(w × review_overall)) ÷ (C + Σw)

C = 10 (configurable by admin). As a product accumulates more reviews, its adjusted score converges toward its true weighted score. Product detail pages always show the raw weighted score; ranking lists use the adjusted score.

Transparency — Both Scores Shown

Product pages always display both the weighted score and the plain unweighted average, so you can see the effect of certification-weighting at a glance.

4.1weighted score·3.7 unweighted avg·12 reviews
Questions about methodology? The entire scoring system is open to inspection. Nothing is black-boxed.