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title: Benchmark Reliability Explorer — saturation, contamination and ranking fragility
description: Explore whether a benchmark gap has limited descriptive resolution, is sensitive to invalid items or potential exposure, sits near the ceiling, or depends on task weighting.
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<section class="s5-page-intro"><div class="s5-eyebrow">Tools · Evaluation · 13</div><h1>Before saying one model wins, check what actually supports the ranking.</h1><p>Two models can differ by a fraction of a point while the result still depends on benchmark composition, a small set of items, a nearly saturated ceiling or test exposure during training. This explorer keeps those failure modes separate instead of compressing them into an opaque reliability score.</p></section>
<div class="s5-tool-summary-strip"><div><small>Resolution</small><strong>score intervals</strong></div><div><small>Integrity</small><strong>invalid items and exposure</strong></div><div><small>Composition</small><strong>weight sensitivity</strong></div><div><small>Boundary</small><strong>benchmark ≠ total quality</strong></div></div>

<div class="s5-tool-workbench">
<form class="s5-tool-controls" aria-label="Benchmark assumptions" onsubmit="return false">
<section class="s5-tool-controls__section"><h2>Evaluation set</h2><div class="s5-tool-field-grid"><div class="s5-tool-field"><label for="s5-bench-items-en">Total items</label><input id="s5-bench-items-en" data-field="items" type="number" min="20" max="10000000" step="10" value="1000" /><small>Binary item scoring is assumed for the descriptive interval.</small></div><div class="s5-tool-field"><label for="s5-bench-invalid-en">Invalid items (%)</label><input id="s5-bench-invalid-en" data-field="invalidRate" type="number" min="0" max="95" step="0.1" value="2" /><small>Broken, ambiguous or incorrectly referenced questions.</small></div><div class="s5-tool-field"><label for="s5-bench-contam-en">Potential test exposure (%)</label><input id="s5-bench-contam-en" data-field="contaminationExposure" type="number" min="0" max="100" step="0.1" value="5" /><small>A sensitivity scenario; it does not claim contamination exists.</small></div><div class="s5-tool-field"><label for="s5-bench-swing-en">Maximum task-weight swing (%)</label><input id="s5-bench-swing-en" data-field="weightSwing" type="number" min="0" max="100" step="1" value="30" /><small>Tests how strongly the winner depends on benchmark composition.</small></div></div></section>
<section class="s5-tool-controls__section"><h2>Tasks and scores</h2><div class="s5-benchmark-table-scroll" role="region" aria-label="Editable task and score table" tabindex="0"><table class="s5-benchmark-table"><thead><tr><th>Task</th><th>Weight</th><th>Model A</th><th>Model B</th><th>Gap</th></tr></thead><tbody><tr data-group-row><td>Reasoning</td><td><input aria-label="Reasoning weight" data-field="w0" type="number" min="0.01" max="100" step="0.1" value="25" /></td><td><input aria-label="Model A reasoning score" data-field="a0" type="number" min="0" max="100" step="0.1" value="82" /></td><td><input aria-label="Model B reasoning score" data-field="b0" type="number" min="0" max="100" step="0.1" value="80" /></td><td><span data-group-gap>—</span><small data-group-share>—</small></td></tr><tr data-group-row><td>Coding</td><td><input aria-label="Coding weight" data-field="w1" type="number" min="0.01" max="100" step="0.1" value="25" /></td><td><input aria-label="Model A coding score" data-field="a1" type="number" min="0" max="100" step="0.1" value="74" /></td><td><input aria-label="Model B coding score" data-field="b1" type="number" min="0" max="100" step="0.1" value="78" /></td><td><span data-group-gap>—</span><small data-group-share>—</small></td></tr><tr data-group-row><td>Knowledge</td><td><input aria-label="Knowledge weight" data-field="w2" type="number" min="0.01" max="100" step="0.1" value="25" /></td><td><input aria-label="Model A knowledge score" data-field="a2" type="number" min="0" max="100" step="0.1" value="86" /></td><td><input aria-label="Model B knowledge score" data-field="b2" type="number" min="0" max="100" step="0.1" value="84" /></td><td><span data-group-gap>—</span><small data-group-share>—</small></td></tr><tr data-group-row><td>Instruction following</td><td><input aria-label="Instruction-following weight" data-field="w3" type="number" min="0.01" max="100" step="0.1" value="25" /></td><td><input aria-label="Model A instruction-following score" data-field="a3" type="number" min="0" max="100" step="0.1" value="79" /></td><td><input aria-label="Model B instruction-following score" data-field="b3" type="number" min="0" max="100" step="0.1" value="78" /></td><td><span data-group-gap>—</span><small data-group-share>—</small></td></tr></tbody></table></div><p class="s5-benchmark-note">Weights are normalized automatically. Interpret them as the share of benchmark items represented by each task family.</p><div class="s5-tool-actions"><button class="s5-tool-action" type="button" data-action="share">Copy scenario</button><button class="s5-tool-action" type="button" data-action="export">Export JSON</button><button class="s5-tool-action" type="button" data-action="reset">Reset</button></div><p class="s5-tool-feedback" data-s5-tool-feedback hidden aria-live="polite"></p></section>
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<section class="s5-tool-results">
<p class="s5-benchmark-interpretation" data-output="interpretation" aria-live="polite">—</p>
<div class="s5-benchmark-kpis"><div><small>Model A</small><strong data-output="scoreA">—</strong><span data-output="intervalA">—</span></div><div><small>Model B</small><strong data-output="scoreB">—</strong><span data-output="intervalB">—</span></div><div><small>Observed difference</small><strong data-output="gap">—</strong><span><span data-output="gapItems">—</span> items of approximate lead</span></div><div><small>Usable items</small><strong data-output="cleanItems">—</strong><span data-output="resolution">—</span></div></div>
<div class="s5-benchmark-grid"><section class="s5-benchmark-panel"><h3>Resolution and saturation</h3><div class="s5-benchmark-pairs"><div class="s5-benchmark-pair"><small>95% interval overlap</small><strong data-output="resolution">—</strong><span>descriptive diagnostic, not a paired test</span></div><div class="s5-benchmark-pair"><small>Headroom to 100%</small><strong data-output="headroom">—</strong><span>less headroom means higher saturation risk</span></div></div><p class="s5-benchmark-note">Aggregate scores do not reveal which exact items each model got right. We therefore do not infer paired significance or manufacture a p-value.</p></section><section class="s5-benchmark-panel"><h3>Dataset integrity</h3><div class="s5-benchmark-pairs"><div class="s5-benchmark-pair"><small>Estimated invalid items</small><strong data-output="invalidItems">—</strong><span>cover the gap? <span data-output="invalidEnvelope">—</span></span></div><div class="s5-benchmark-pair"><small>Potentially exposed items</small><strong data-output="exposureItems">—</strong><span>cover the gap? <span data-output="contaminationEnvelope">—</span></span></div></div><p class="s5-benchmark-note">These are worst-case envelopes: they ask whether that number of items could explain the lead if every one favored the leader. They are not evidence of contamination or broken scoring.</p></section><section class="s5-benchmark-panel"><h3>Composition sensitivity</h3><div class="s5-benchmark-pairs"><div class="s5-benchmark-pair"><small>Gap range after reweighting</small><strong data-output="weightRange">—</strong><span>minimum → maximum</span></div><div class="s5-benchmark-pair"><small>Ranking</small><strong data-output="weightStatus">—</strong><span>all weights are renormalized</span></div></div><p class="s5-benchmark-note">The calculation evaluates the extreme ± combinations for the selected percentage across all four task families. A winner flip shows dependence on which tasks we decide to emphasize.</p></section><section class="s5-benchmark-panel"><h3>Triggered fragilities</h3><div class="s5-benchmark-flags" data-output="flags"></div><p class="s5-benchmark-note">We do not add these signals into a single “reliability index.” Saturation, contamination, statistical resolution and composition are different problems that require different evidence.</p></section></div>
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<section class="s5-section"><div class="s5-section-head"><div><div class="s5-eyebrow">Method</div><h2>What this explorer measures — and what it does not</h2></div></div><div class="s5-benchmark-method"><div><strong>Descriptive interval</strong><p>A 95% Wilson interval is computed from the aggregate score and usable items. The approximation assumes binary scoring and that weights represent item shares. If task families use different metrics, or both models answer the same items, per-item data and an analysis matched to the evaluation design are needed.</p></div><div><strong>Contamination sensitivity</strong><p>The score gap is converted into an approximate number of items and compared with a hypothetical exposure. This is a sensitivity bound, not contamination detection.</p></div><div><strong>Benchmark lottery</strong><p>Reweighting task families shows whether ranking depends on task selection. There is no universally correct weighting outside the deployment objective.</p></div><div><strong>Holistic evaluation</strong><p>Accuracy alone does not cover robustness, calibration, efficiency, safety or deployment fit. This tool evaluates benchmark ranking claims, not total model quality.</p></div></div></section>
<section class="s5-section"><div class="s5-note-feature"><div><div class="s5-eyebrow">Sources</div><h2>A leaderboard needs statistical and methodological context.</h2><p>The Benchmark Lottery shows that changing tasks can alter rankings. HELM argues for broad coverage, multiple metrics and explicit recognition of what is missing. LiveBench addresses contamination directly through frequently updated questions and objective scoring.</p></div><div class="s5-note-feature__meta"><a href="https://arxiv.org/abs/2107.07002">Dehghani et al. · The Benchmark Lottery</a><br /><a href="https://crfm.stanford.edu/2022/11/17/helm.html">Stanford CRFM · HELM</a><br /><a href="https://arxiv.org/abs/2406.19314">LiveBench · Contamination-Free Benchmark</a><br />Reviewed: 2026-08-21</div></div></section>
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