Chapter 5

Deviating from the Average


Finding out what variation is all about

Working with variance and standard deviation

Exploring Excel worksheet functions that calculate variation

Using workarounds for missing worksheet functions

Using additional worksheet functions for variation

Here are three pieces of wisdom about statisticians:

Piece of Wisdom #1: “A statistician is a person who stands in a bucket of ice water, sticks their head in an oven and says ‘on average, I feel fine.’” (K. Dunning)

Piece of Wisdom #2: “A statistician drowned crossing a stream with an average depth of 6 inches.” (Anonymous)

Piece of Wisdom #3: “Three statisticians go deer hunting with bows and arrows. They spot a big buck and take aim. One shoots and his arrow flies off ten feet to the left. The second shoots and his arrow goes ten feet to the right. The third statistician jumps up and down yelling, ‘We got him! We got him!’” (Bill Butz, quoted by Diana McLellan in Washingtonian)

What’s the common theme? Calculating the mean is a great way to summarize a group of numbers, but it doesn’t supply all the information you typically need. If you just rely on the mean, you might miss something important.

To avoid missing important information, another type of statistic is necessary — a statistic that measures variation. It’s a kind of average of how much each number in a group differs from the group mean. Several statistics are available for measuring variation. All of them work the same ...

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