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# S1 - What is Variance / Standard Deviation ? watch

1. Recapping the earlier units and I've seemed to misplace my notes on the topic. Am I right in saying Variance is how far the values are out from the overall mean ? And Sd is just the root of it ?
2. yes, variance measures the variation around the mean.
StD is the square root of it!
3. (Original post by WildBerry)
Recapping the earlier units and I've seemed to misplace my notes on the topic. Am I right in saying Variance is how far the values are out from the overall mean ? And Sd is just the root of it ?
I'd rather say that Standard Deviation measues how far values tend to lie away from the mean, and variance is the square of it. If you measure peoples' height in metres, the standard deviation will also be in metres. It might be 0.1 m, say, and will mean something in real life. You can often estimate the SD of a distribution by eye. I can't give a useful physical meaning to variance, although it has some nice algebraic properties. It would have units in this case of m^2.

Technically - Standard Deviation is the Root Mean Square deviation from the mean.

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