How Accurate Is This Source? A Step-by-Step Guide for students

Learning to ask "can I believe this?" is one of the most important skills in history. This guide breaks down how to check whether a historical source is accurate — in simple steps, with sentence starters you can use right away.

What does "accuracy" mean in history?

Imagine two students both tell you a different story about something that happened in the playground at lunch. Which one do you believe? To figure that out, you'd probably ask: who saw it happen? Does anyone else agree with their version? Does their story even make sense?

That's exactly what historians do with historical sources. Accuracy means working out how correct the information in a source actually is.

You can never be 100% sure — and that's okay

Here's something important: historians almost never say a source is "100% accurate" or "completely false." Instead, they talk about a degree of accuracy — like a sliding scale.

Extremely accurate	Very accurate	Somewhat accurate	Rarely accurate	Not very accurate
Matches other evidence almost perfectly	Mostly matches, small gaps	Some correct, some questionable	Mostly contradicted by evidence	Strongly contradicted or clearly biased

Using this scale in your writing makes you sound like a real historian — instead of just saying "this source is accurate," try saying "this source is somewhat accurate" and then explain why.

Three questions to ask about any source

Whenever you need to check a source's accuracy, run through these three questions:

1. Does another source agree with it? (This is called corroboration.)
2. Does the source show signs of bias that might make someone twist the truth?
3. Does the information actually make sense, based on what else you know?

How to Argue That a Source IS Accurate

The strongest way to argue a source is accurate is to find another source — especially a more trustworthy one — that says the same thing. This is called corroboration, and it's your best tool.

Here are three ways to build that argument:

Reason	Why It Works
It's corroborated	A separate, trustworthy source says the same thing — the strongest evidence you can use
The audience would have known the truth	If the creator was writing for people who were there or already knew the facts, it would be risky to lie to them
The purpose was to record facts honestly	Some sources — like official records — were created specifically to be accurate, not to persuade anyone

Real example

The ancient Greek writer Herodotus described the weapons and armour worn by Persian soldiers in his histories. For a long time, some historians doubted his accounts because parts of his writing seemed exaggerated. But archaeologists later dug up Persian weapons and armour that matched his descriptions almost exactly — corroborating what he wrote, even though he was writing from secondhand reports, centuries before modern record-keeping.

How to Argue That a Source Is NOT Accurate

Finding inaccurate information in a source is not a failure on your part — it's actually a sign of strong historical thinking. Don't be afraid to point out when a source gets something wrong. Markers and teachers want to see you notice this.

Reason	Why It Works
It's contradicted	A separate, more trustworthy source says something different — strong evidence of inaccuracy
There's obvious bias	The source clearly favours one side and ignores or unfairly twists the other perspective

Real example

During the First World War, Hitler later claimed that Jewish soldiers had undermined the German war effort. This claim is contradicted by the historical record: a large number of Jewish soldiers actually received military awards for bravery during the war. The evidence directly disproves the claim — making it a clear case of an inaccurate, and clearly biased, source.

Going Deeper: Sources Can Be Part Right, Part Wrong

This is the most advanced — and most realistic — idea on this page. Most historical sources are not entirely accurate or entirely inaccurate. They are usually a mix.

Think about a soldier's diary from a war. The soldier was really there, so their description of what the battlefield looked like might be very accurate. But they might also be wrong about how many enemy soldiers there were, because in the chaos of battle, it's easy to overestimate. The same source can be accurate about one thing and inaccurate about another.

Why this happens

• The writer may not have known everything — they could only see and understand part of the full picture
• The writer may have had a bias that shaped how they described certain people or events
• Time can distort memory — sources written long after an event are more likely to contain mistakes

⚠️ Don't Mix Up Accuracy and Reliability

This is the trickiest — and most important — idea on this page. A source can have mistakes and still be reliable. That sounds strange at first, but think about it this way:

Imagine a soldier's diary that gets one date wrong but gives an honest, detailed, firsthand account of daily life in the trenches. That single date error doesn't suddenly make the entire diary worthless. The source is still extremely valuable — and still largely reliable — even though it contains one inaccuracy.

	Accuracy	Reliability
The question it answers	Is the information correct?	Can I trust this source overall?
One small error means…	Less accurate, in that one spot	Doesn't necessarily change much at all

Always check accuracy and reliability separately — never assume that because one is low, the other must be too.

Quick Recap

• Accuracy means judging how correct the information in a source is
• Use a scale of degree: extremely → very → somewhat → rarely → not very accurate
• The strongest evidence for accuracy is corroboration — another source agreeing
• The strongest evidence for inaccuracy is contradiction — another source disagreeing
• Finding an inaccuracy is not a problem — explaining why it happened shows excellent historical thinking
• A source can be accurate about one thing and inaccurate about another
• Accuracy and reliability are not the same thing — always check them separately