# What is ground truth in AI?

> Ground truth is the known correct answer you check AI output against, such as your real price list or the actual invoice total.

Source: https://learn.ynteractive.com/content/glossary/ground-truth · Updated 2026-10-20 · Free from Stepthrough (https://learn.ynteractive.com)

[AI basics](https://learn.ynteractive.com/content/glossary#topic-ai-basics) · [AI glossary](https://learn.ynteractive.com/content/glossary)

Quick answer

Ground truth is the known correct answer or record that you measure AI output against: the real invoice total, the price on your price list, what the contract actually says. Without ground truth you can't tell whether an AI answer is right; you can only tell whether it sounds right.

Last updated October 20, 2026

[Take the free module →](https://learn.ynteractive.com/courses/voice-ai-jump-start/2)Module 2 of the free [Voice AI Jump Start](https://learn.ynteractive.com/courses/voice-ai-jump-start) course, about 8 minutes. No account needed.

Updated October 20, 2026 · By [Robert Breen](https://learn.ynteractive.com/content/about)

## Why it matters for a small business

Every check in these lessons is a ground-truth check: compare the quote with the fact sheet, the row with the receipt, the citation with the page. AI makes the work faster, but the comparison with a known-correct source is what makes it safe.

For testing a prompt or agent at scale, build a small set of examples with the correct answers written down. Run the AI on them and count how many match. That gives you a number you can watch when you change the prompt or the model.

## In a real lesson: ElevenLabs vs Vapi: Cost per Call and a Launch Checklist

In [ElevenLabs vs Vapi: Cost per Call](https://learn.ynteractive.com/content/elevenlabs-vs-vapi-cost-per-call-launch-checklist), you give ChatGPT the prices from each pricing page and Cedar Creek Plumbing's 360 minutes a month, and tell it to use only those numbers and show its math. Those pricing pages are the ground truth.

ChatGPT's first table leaves out the Twilio phone line for ElevenLabs, which makes the two platforms look identical. Because you have the real prices, you catch it, and one correction gives $36.61 a month for ElevenLabs and $32.40 for Vapi.

[Try this lesson free](https://learn.ynteractive.com/modules/voice-agents-compare-launch) or [read the step-by-step guide](https://learn.ynteractive.com/content/elevenlabs-vs-vapi-cost-per-call-launch-checklist).

## Common confusions

### Ground truth vs source of truth

A source of truth is the system where a record officially lives, like your accounting app. Ground truth is the correct answer you test against, which often comes from that source.

### Ground truth vs training data

Training data teaches a model. Ground truth checks it. The same labeled examples can serve either purpose, but keep test examples out of training.

## Tips

- Keep the original document open next to the AI's answer.
- For repeated jobs, save ten examples with the correct answers as a test set.
- Check totals with a calculator or spreadsheet formula, not another AI answer.

## Related terms

[Source of truth](https://learn.ynteractive.com/content/glossary/source-of-truth) · [AI evals](https://learn.ynteractive.com/content/glossary/ai-evals) · [Test data](https://learn.ynteractive.com/content/glossary/test-data) · [AI math errors](https://learn.ynteractive.com/content/glossary/ai-math-errors) · [Hallucination check](https://learn.ynteractive.com/content/glossary/hallucination-check)

## More AI basics terms

[Grounding](https://learn.ynteractive.com/content/glossary/grounding) · [Hallucination](https://learn.ynteractive.com/content/glossary/hallucination) · [Inference](https://learn.ynteractive.com/content/glossary/inference) · [Intelligent document processing](https://learn.ynteractive.com/content/glossary/intelligent-document-processing)

## Where you use it: free lessons

- [ElevenLabs vs Vapi: Cost per Call and a Launch Checklist](https://learn.ynteractive.com/content/elevenlabs-vs-vapi-cost-per-call-launch-checklist) (ChatGPT, 8 min)
- [Stop Losing Context: When to Start a New Chat vs Keep Going using ChatGPT](https://learn.ynteractive.com/content/chatgpt-stop-losing-context-new-chat-vs-keep-going) (ChatGPT, 9 min)
- [AI Receipt Extractor: Receipts to Google Sheets with n8n](https://learn.ynteractive.com/content/ai-receipt-extractor-n8n-google-sheets) (n8n, 12 min)

## Frequently asked questions

**Where does ground truth come from?**

From records you trust: your price list, the signed contract, the bank statement, or answers a careful person has checked.

**Do I need ground truth to use AI?**

You need it for anything that matters. Without a known-correct reference, you can't tell a right answer from a confident wrong one.

**What is ground truth in machine learning?**

The correct labels or answers used to train and test a model, such as receipts labeled with their real category.

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