--- title: Why 90% Accuracy Doesn’t Mean You Should Trust an AI Model description: A 90% accuracy score on an AI model can be deeply misleading. Using medical AI as the context, this piece walks through two concrete failure modes: a model... canonical: https://daily.dev/posts/why-90-accuracy-doesn-t-mean-you-should-trust-an-ai-model-vttihmbg7 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Why 90% Accuracy Doesn’t Mean You Should Trust an AI Model | daily.dev og:description: A 90% accuracy score on an AI model can be deeply misleading. Using medical AI as the context, this piece walks through two concrete failure modes: a model... og:url: https://daily.dev/posts/why-90-accuracy-doesn-t-mean-you-should-trust-an-ai-model-vttihmbg7 og:image: https://api.daily.dev/og/posts/VTTIHMbG7.png og:image:alt: Why 90% Accuracy Doesn’t Mean You Should Trust an AI Model og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Why 90% Accuracy Doesn’t Mean You Should Trust an AI Model **[Medium](https://daily.dev/sources/medium_js)** · 8 min read · 0 upvotes · 0 comments ## Summary A 90% accuracy score on an AI model can be deeply misleading. Using medical AI as the context, this piece walks through two concrete failure modes: a model that achieves 99% accuracy by never detecting a rare disease, and a model that is accurate overall but wildly overconfident in its predictions. It frames evaluation metrics — precision, recall, F1, AUROC, and calibration — not as competitors but as a sequential journey, each covering a blind spot the previous metric couldn't see. The key insight is that intelligence and honesty are independent properties: a model can rank patients well while still overstating its confidence, and no single number captures both. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### why is a 90% accurate model not necessarily trustworthy for medical diagnosis High accuracy can hide two failure modes: the model may never detect the rare condition it exists to find, or it may overstate its confidence while still being right 90% of the time. Accuracy only measures overall correctness, not whether sick patients were caught or whether stated probabilities are honest, so it cannot distinguish a blind model from a reckless one. _Anyone weighing whether to trust a new model's reported accuracy can find deeper evaluation breakdowns on daily.dev._ ### what does a 99% accuracy score mean if a disease only affects 1% of patients It can mean the model caught zero of the sick patients. In a screening scenario of 1,000 patients where only 10 have a rare condition, a model that labels everyone healthy is right 990 times out of 1,000, yielding 99% accuracy while missing every actual case, because accuracy mostly rewards correctly predicting the common outcome. _Developers building rare-event classifiers can track evaluation pitfalls like this one through daily.dev._ ### what is the difference between AUROC and calibration when evaluating a model AUROC measures how well a model ranks patients by risk across all possible thresholds, while calibration measures whether the model's stated confidence matches reality, such as whether predictions labeled 90% confident are actually correct 90% of the time. A model can have excellent AUROC while still being badly miscalibrated and overconfident. _Teams choosing which metrics to trust when comparing models can follow evaluation deep dives on daily.dev._ ## Similar posts on daily.dev - [What If the AI Is Confident - and Wrong?](https://daily.dev/posts/what-if-the-ai-is-confident---and-wrong--z2x2jxp1q) · Medium · 0 upvotes · 0 comments - [The AI Model Confidence Trap](https://daily.dev/posts/the-ai-model-confidence-trap-93to0xhgy) · Towards Data Science · 5 upvotes · 1 comments - [Health-care AI is here. We don’t know if it actually helps patients.](https://daily.dev/posts/health-care-ai-is-here-we-don-t-know-if-it-actually-helps-patients--3lz9zsugd) · MIT Technology Review · 0 upvotes · 0 comments - [Don’t Let the Model Grade its Own Homework](https://daily.dev/posts/don-t-let-the-model-grade-its-own-homework-k8meawh6n) · SD Times · 1 upvotes · 0 comments - [In Harvard study, AI offered more accurate diagnoses than emergency room doctors](https://daily.dev/posts/in-harvard-study-ai-offered-more-accurate-diagnoses-than-emergency-room-doctors-cregqshlt) · TechCrunch · 1 upvotes · 0 comments --- Tags: [#machine-learning](https://daily.dev/tags/machine-learning), [#data-science](https://daily.dev/tags/data-science) [View this post on daily.dev](https://daily.dev/posts/why-90-accuracy-doesn-t-mean-you-should-trust-an-ai-model-vttihmbg7) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Why 90% Accuracy Doesn’t Mean You Should Trust an AI Model","url":"https://daily.dev/posts/why-90-accuracy-doesn-t-mean-you-should-trust-an-ai-model-vttihmbg7","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/why-90-accuracy-doesn-t-mean-you-should-trust-an-ai-model-vttihmbg7"},"datePublished":"2026-07-26T02:44:46.171Z","dateModified":"2026-09-14T07:27:16.363Z","description":"A 90% accuracy score on an AI model can be deeply misleading. 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