Presenting Data and Statistics

This famous statistical graphic shows the losses of Napoleon's army as it attempted to invade Russia in 1812. The thick band shows the army as it goes in, and then as it retreats, decimated, the thin dark low band). The graphic does ALL the work of telling the story.

When numbers are what you need to communicate to your audience,  they must not overwhelm. • Don’t overload your audience with statistics. Tell them the story that the numbers reveal, don’t dwell on the numbers themselves. Give them just enough to get the point across. You can always give them additional data if they ask for it. • Choose meaningful data. Try to choose data that show the magnitude of the problem, data that provide context or meaning, and data that are new or noteworthy. • Avoid statistical terminology  – there are simpler ways to explain results. Most people have low maths literacy, even the highly educated. Unless you’re communicating to scientists, the term “statistically significant” is rarely meaningful. Instead, say “more likely” or “less likely.” • Avoid data terms like p-value, confidence limit, correlation, regression, and chi square. Instead, try to say things like number, count, percent, rate, and average. These are data terms almost anyone can understand. • Turn numbers into words. For example, instead of presenting an odds ratio as 2.0, say that smoking doubles the risk of having a heart attack. Even with relatively simple data, like percents, it can be useful. Instead of saying “25% of children do not wear seatbelts,” say “one out of every four children does not wear a seatbelt.” This is a more clear and helpful way of saying the same thing. Slides and Handouts In a presentation you have three channels of communication available to you. One is you, the speaker and your words, the second is the slides and the third is the handout. Most statistically heavy presentations fail because the presenter has put too much data in the slides and forgotten that a handout is a better vehicle for carrying this sort of detailed information. Put a few pages on the seats before you start, if you really need to refer to some details. Keep the slides simple, use ‘glanceable’ images. Good graphs Graphs are a fantastic shortcut for presenting data. Edward Tufte is the guru of presenting statistical information visually. He coined the term ‘Chartjunk’ and his mantra is ” Minimise the non data ink” . If you are using a pie chart on a slide keep it to 6 slices. A table should have only 4 lines. Colour scales need to be intuitive – not random or decorative, they carry a meaning, and don’t use 3D effects and other decorative fillers and frills unless they serce a communicative purpose.