Whether it is pointing out a politician's big whopper of a lie or highlighting misleading information published by the media themselves, the aim is to ensure audiences have accurate information upon which to make responsible decisions, particularly when you consider the damage a claim could have if left unchecked.
At the Poynter Fact-Checking Global Summit in London yesterday (9 May), Angie Holan, editor of PolitiFact, ran a session in best practise for fact-checking.
So if you are faced with a statement from a public official where the numbers sound a little bit fishy, here are some of her tips on whether it is worth investigating, and how to get the evidence to refute it.
1. Is it a fact or an opinion?
Sometime it is a tough call between fact and opinion. Factual statements can be inflective with opinions, while statements of opinion can also be based on incorrect facts.
Juliette Jowit, who runs the Guardian's Reality Check blog, fact-checked a report earlier this year claiming that that the 'cost of living' crisis was over and received a lot of pushback from readers about whether this claim could be fact-checked.
She said the numbers given in several reports showed that living standards were rising, and that this statement was worth fact-checking as it is still Labour's key election message.
If the statement was found false, she said, Labour would face a much bigger challenge to convince people that there still is a crisis.
Not all readers agreed with her findings though, with some implying that her evidence lacked context as just because the numbers were going up, it did not mean people's individual experiences were getting better.
Fact-checking should always be carried out in context, Holan advised.
2. You cannot fact-check predictions
It is impossible to fact-check predictions, according to Holan, as they clearly are not facts. However, journalists should fact-check casual statements which may be based on wrong information.
For example, earlier this month PolitiFact checked statements from Obama's administration that new carbon regulations would increase electric bills by "$17 billion every year" and "potentially put an average of 224,000 more people out of work every year".
The outlet found that the statements were based on findings from a study that was not reflective of what was actually proposed.
3. The speaker's intentions (then or now) are irrelevant
Journalists should not allow their judgement to be clouded by a person's intention at the point a claim was made. For example, the Liberal Democrats may have had good intentions when they promised to scrap tuition fees, but they still broke their campaign promise.
PolitiFact has a Truth-O-Meter that rates whether politicians fulfilled their campaign pledges once in office. "On our meter, we rate outcomes, we don't rate intentions," said Holan.
4. Reach out to the statement maker first
At the Poynter summit, there was some debate over whether people should reach out to the person who made the statement they are fact checking to help with verification.
Holan believes the speaker should be the first person you go to – out of fairness, but also because they might they be able to provide you with the evidence they used for the basis of their claim.
Approaching the speaker early is also best, she said, in order to reduce the risk of having to delay publication of a story because you are still waiting for their respose.
"I think it's only fair to contact the speaker and give them the chance to give their point of view, but I say this as someone from a country with a lot of press freedom," Holan said.
"I have no worries about dubious influence, them influencing my editors, but I've spoken to people who say if we call the speaker first they can do all sorts of things – threaten your physical security, call your editor, just to kill the fact check".
"But I will always contact the press secretary of whoever I'm fact-checking as soon as I begin my research, just saying 'I wanted to let you know as soon as possible we're fact-checking this, can you send us your evidence of the Congressman saying this?'
Holan added she would then contact the speaker's office again before publication to share her key findings.
5. Check your archives (and others)
As with any news story, Holan said journalists should check if the story has been covered before, or if a false fact has already been debunked.
She recommended Nexis and Wayback Machine as useful tools for checking old news archives and websites. Google is also a must too, as it can be used to find out what issues other people outside news organisations have found with a claim.
6. Find experts – on both sides
Journalists should look for expertise on the subject area around the statement you are trying to disprove, Holan said.
Representatives from fact-checking organisations at the summit who were surveyed said this expertise most often came from government reports and interviews with subject experts, followed by think tank reports and reviewing public laws and statutes. You can also make use of online library resources like WorldCat.org.
Looking for bias in any reports is also really important ,and Holan advised fact-checkers to ask a subject expert for recommendations of their opposites in the field: "Is there anyone who studies this topic who you respect who disagrees with you?"
7. New claims vs old
It can be tempting to go after new exciting claims to fact-check, but chasing the old ones that keep popping up are just as important to confirm or dispute.
Holan said: "I love new claims – when no one knows whether it's true or not and we're going to find the truth and shine a light on it, but on the other hand there's a lot of bullshit that gets recycled that still needs to be debunked.
"Not every fact-check is going to see the world on fire… but I think with information that keeps getting repeated and it's wrong, you should keep repeating the fact-check."
Asked if it's worth fact-checking a statement another organisation has already done, Glenn Kessler, fact checker columnist for The Washington Post, offered the point that doing so added further authority to everyone's work: "If all three of [the main fact-checking organisations] in the States say this fact is wrong, it has much so more impact."
How do you decide which claims you should invest more time on verifying? Holan said how relevant a fact is to your readers is really important – do not fact-check something boring, she said, fact check what people care about and what is timely.
When surveyed, the fact-checking organisations at the summit said that readers and transcripts were the most common sources for them of finding facts to check.
Julian Rademeyer, editor of AfricaFact, agreed – "When we crowdsource claims to fact-check we always ask our users to explain the impact this claim would have if left unchecked."