i googled it, but still understood nothing 😛
What’s this thing??
In: Mathematics
Once you have an average, the standard deviation is “how far away from average are people, typically?”.
If you count how many heads people have, the average is 1 and the standard deviation is basically zero. Most people’s head number is zero units away from the average.
If you count how many fingers people have, the average is 9.98-ish (I’m making these numbers up) and the standard deviation might be 0.02. Most people are very close to the average number, but thanks to polydactyly and table saws there is some variation.
If you have a test where half the class got 0 and the other half got 100, your average is 50, but your standard deviation is also going to be about 50, because all your people are very far away from the average. (Everybody, in this example, is either 50 above or 50 below the average.)
In other words, a small standard deviation means “this average represents the group really well; most people are only a small distance from the average” and a big standard deviation means “this average is not a good representation of the group; many people are a big distance from the average”.
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