Good evidence comes from good sources. Anyone can publish online, so before you trust a source, check it.
| Ask | Look for |
|---|---|
| Who wrote it? | an author or organization with real knowledge of the subject |
| What evidence does it give? | data, named sources, links you can follow |
| When was it written? | a date recent enough for the topic |
| Why was it written? | to inform, or to sell, persuade or entertain? |
| Do other good sources agree? | the same facts in independent, reliable sources |
Key idea
Judge a source by its author, its evidence, its date, its purpose, and whether other good sources agree. A source that is clear about who made it and where its facts came from earns more trust.
Why it works
Your essay is only as reliable as its sources. A reader who finds one weak source starts to doubt the rest. Purdue OWL’s guides to evaluating sources ask the same kinds of questions: the author’s background, the date, the evidence, and the purpose or bias.
Worked example: Compare two sources
For a report on how much sleep teens need: (a) a CDC report that cites the American Academy of Sleep Medicine, or (b) a mattress company’s blog post. Which is stronger?
- (a) comes from a public health agency and names its expert source.
- (b) comes from a company that sells mattresses: its purpose is to sell.
- The blog may be right, but you would want to confirm it elsewhere.
Answer: (a), the CDC report.
Worked example: Is the date a problem?
A 2009 article lists “the newest phones.” A 2009 article explains how the heart pumps blood. Which date matters more?
- Phones change every year, so a 2009 list is out of date.
- How the heart works hasn’t changed.
Answer: The date matters for the phone article, much less for the heart article.
Common mistake
Trusting a source because it looks professional or came first in a search. Design and search rank don’t show accuracy. Check by leaving the page: search for the author and the organization, and look for the same facts in another reliable source.
Encyclopedias are good places to start and to find sources, but cite the sources they lead you to when you can. On this site we use primary and official sources first.