I saw a great slide deck by Edward Kavanaugh titled Statistics Without Context on SlideShare. I have embedded the whole presentation at the bottom of this post. [Update: Ed Kavanaugh is entered in a presentation contest. If you like this post, please click here to vote for his presentation. There is a green thumbs up icon that allows you to vote. ]
First, what is context?
The context is the circumstances in which an event occurs.
If you are asked, “How many apples did you buy?”
“20% more than yesterday!” might be the answer from an annoying person.
20% is just a statistic. What you bought yesterday is the context. You need to know that 10 apples were bought yesterday to know that 12 apples were bought today.
Edward provides three examples of claims:
He then puts these statistics in context:
- 5 out of 100 people contract colorectal cancer.
- If incidence rose by 20%, that would be 1 more person for a total of 6 (5 x 120% = 6)
- So, “Bacon increases risk of colorectal cancer by 20%” is the same as saying it causes 1 more case in 100.
Edward then goes through the same analysis for the other two claims. In the end:
Unless you add some context to the percentage, there is no meaning.
You can see the whole presentation below.
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This post filed in the following categories:
- Best of Simple Complexity - The best posts of Simple Complexity as judged by the post authors.
- Statistics - Statistics is a mathematical science pertaining to the collection, analysis, interpretation or explanation, and presentation of data.
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now that its done i wonder if its good enough to join the list !"
He did one small mistake, unfortunately everyone does mistakes."
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Hey Neal,
I am a biiiig fan of the blog so its quite an honour to be included on it!
I really feel passionately about promoting understanding of statistics and I am quite tired of the constant abuse of numbers by the media in general.
For any slideshare users please click through and give it a vote for the presentation comeptition! (shameless plug over)
Ed
If you liked this, then it’s likely you will appreciate the slideshow that helped to inspire Ed Kavanagh above. You can find it here http://news.bbc.co.uk/1/hi/magazine/7937382.stm
Written by Michael Blastland, the graphics were produced by BBC news website design team. It’s Michael’s mission to help us all make sense of numbers and his regular column on the BBC news website is a great read.