Last week was World Statistics Day, and while you might not have celebrated this less-than-beloved global holiday, maybe you should have. As the world has grown more complex, data helps us understand what's truly going on and make wise decisions. It also can be manipulated to make political points, deceive others, and reinforce existing biases

Which is why writer and economist Tim Harford decided to mark the occasion with a long Twitter thread on how to both communicate clearly with numbers and avoid being taken in by other people's data-powered BS. 

As the author of the new book How to Make the World Add Up, Harford is ideally placed to offer these lessons and because he did it via Twitter his wisdom is so succinct you have no excuse not to remember it. So here, for easier reading and continued reference, is Harford's extremely useful advice. 

1. Search your feelings. 

"What we believe, or refuse to believe, is strongly influenced by our emotional reaction. A lot of the statistical claims we see aren't just data: they are weapons in an argument. Social media thrives on emotion. So do media headlines," Hartford cautions. 

You can't escape your emotions, but you can notice and attempt to correct for them. "If the reaction to a claim is a knee-jerk, 'this proves I was right!' or 'Fake news,' we need to count to three and start thinking more clearly," Harford recommends. 

2. Ponder your personal experience.

"We get information from graphs and spreadsheets. We also get information from the rich and vivid experiences all around us," Harford writes. "Often our personal experience conflicts with the data. Sometimes the data are misleading. Sometimes it's our own experience that is skewed in some way. One thing I learned from the great [data wizard and beloved TED speaker] Hans Rosling was that the best insights come when we are able to combine the two."

3. Avoid premature enumeration.  

Harford offers this warning to the data nerds among us: "One of the perils of being numerate is the temptation to start chopping up numbers -- computing ratios, rates of increase, means and variances -- before we understand what they refer to."

"Arguably the financial crisis of 2007-08 was caused, in part, by very sophisticated mathematical analysis of measures of risk which were poorly understood. Start by understanding what the numbers refer to, eh?" he urges.

4. Step back and enjoy the view.

You know that cartoon where several blindfolded people are touching an elephant and coming up with very different interpretations of what they're feeling. The guy at the tail thinks he's got his hands on a rope. The one at the flank figures he's facing a wall. Well, the same phenomenon can happen if you latch onto a single number. 

"Rather than focusing on the latest data point, get some context. What has happened to this data series over the past year? Past decade? What is happening elsewhere? Are there any comparisons which help make sense of the number?" Harford suggests. 

5. Get the backstory

Along similar lines to the point above, Harford also advises people to think about the human origin of the statistics they hear.

"Every number is in front of your eyes for a reason -- often because it is particularly surprising. It may be surprising because it is not representative of a wider trend. It may be surprising because it is flat-out wrong," he says. "The 'replication crisis' in psychology came about as scholars realized that peer-reviewed work was subject to a powerful 'interestingness' filter -- good-but-dull work was buried, while flukes were published. But that same powerful filter, publication bias, is everywhere."

6. Ask who is missing 

Data is only as good as the representativeness of the sample it's coming from. Overlook people or groups and conclusions quickly get skewed. To learn more about the phenomenon, he recommends the book Invisible Women by Caroline Criado Perez. 

It's about "how the data we gather often miss the needs of women, or fail to disaggregate so that we can ask questions about the different experiences of women and men," he explains. "Once you start thinking like that, you see data gaps everywhere -- from the shy Trump voters who pollsters missed at the last election, to grand big-data based claims that only measure those of us with smart-phones." 

7. Demand transparency when the computer says no.

"Algorithms are providing some amazing insights -- but very often they are commercially confidential," Harford explains in this tip that's particularly relevant for business leaders. "Senior managers and politicians swallow tall tales about the power of the algorithm ... but those grand claims are often unproven. We should demand better evidence and independent scrutiny."

8. Don't take statistical bedrock for granted.  

It's possible to lie and obfuscate with numbers, but can you imagine making tough decisions without data? We need to be cautious about statistics, but we shouldn't forget to appreciate them and those who gather and crunch the data to produce them.

"All around us, statisticians and other hero-geeks are painstakingly gathering and analyzing the numbers we need to understand what is happening all around us," Harford writes, citing all the scientists rushing to get a handle on the current pandemic as one extremely topical example. 

"The statistics are quietly and carefully assembled and we take them for granted. We just assume they will always be there when we need them. We notice only when something goes wrong. That is a shame. So let us celebrate the wonderful folks who help us see the invisible all around us," he urges. 

9. Remember that misinformation can be beautiful too. 

Just because a chart looks polished and definitive doesn't mean it's correct. 

"There is a risk in data-visualisations," warns Harford. "[How Charts Lie author] Alberto Cairo points out that our visual sense is so potent we use phrases such as 'I see' as a synonym for 'I understand.' Very often, however, the understanding is illusory -- we've been fooled by beauty. All the other rules apply, with double force, when looking at a picture of data."

10. Keep an open mind. 

"Easy to say, isn't it? But what I mean here is a willingness to keep examining the data and being able to admit to yourself and others that you have changed your mind," says Harford. That's great advice whatever the question or claim you're trying to evaluate. 

Intrigued by Harford's advice? Then off to the bookstore with you to pick up his book.