i googled it, but still understood nothing 😛
What’s this thing??
In: Mathematics
You’re probably familiar with the concept of an average or *mean*. In some sense, the mean tells you “where your data is” – is it mostly big or small, is it close to 0 or far away, etc.
Standard deviation tells you *how far from the mean your data is* on average. It’s a measure of how “spread out” your data is – a high standard deviation means your data is spread out, a low standard deviation means it’s piled up close to the mean. It’s a tad more complicated than this, but that’s the way you want to think about it conceptually.
Mathematically, you get the standard deviation by figuring out how far each point is from the mean, squaring those distances, averaging them, and then taking the square root. For example, if you have five people whose heights are {50, 55, 60, 65, 70}, we can easily compute the mean (60). Then the distances from the mean are {10, 5, 0, 5, 10}. Squaring these gets us 100, 25, 0, 25, 100, and averaging those gets us 50. Then the square root of 50 – about 7 – is our standard deviation.
Compare that to a different collection of heights, say, {60, 70, 80, 90, 100}. This collection has a larger standard deviation of about 14. We can interpret this as saying that the second collection {60, 70, 80, 90, 100} is in some sense “more spread out” than the original collection {50, 55, 60, 65, 70}.
Latest Answers