08 May 2005

How to lie with statistics

We had a departmental seminar on Friday. It was good, but the speaker got under my skin with one silly claim. She was discussing how life expectancy is 36 or so in a region in Africa where she works. So she asked for a show of hands of everyone in the room who was over that age. After a fair chunk of the room did so, she said, "All dead."

Rhetorically effective, but wrong. If average height is 5'8", does everyone stop growing at 5'8"? An average represents the middle of a sample. Some people will be above average and some are below average. Heck, depending on the distribution, the majority could be above average!

And she knew better, which was the most annoying thing.

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