- #1

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## Main Question or Discussion Point

OK I was going to post this in homework, but it's not homework (left school a long time ago ;))

Anyway when I was at school I did not do stats I did mechanics instead (you had a choice).

However all the people doing stats were always on about the the SD, which was a bit annoying

cos I didn't know what it was.

Anyway I asked one guy who did stats what it was, and he did not seem to give a very convincing/good answer, I think he said it was so many percent or something like that.

OK so I looked on wiki and it gives a definition

SD = is the square root of its variance

and:-

variance of a random variable or distribution is the expectation, or mean, of the deviation squared of that variable from its expected value or mean.

OK.......so I can understand how to calculate it however.... I don't understand *why* you would want to calculate that?

Why not take the cube root of the variance, or 1/variance or log(variance) or sin(variance)

or indeed any other function you can think of???

I just do not see what is significant about the square root of the variance!!

Hope this is not a 'stupid question' :)

Anyway when I was at school I did not do stats I did mechanics instead (you had a choice).

However all the people doing stats were always on about the the SD, which was a bit annoying

cos I didn't know what it was.

Anyway I asked one guy who did stats what it was, and he did not seem to give a very convincing/good answer, I think he said it was so many percent or something like that.

OK so I looked on wiki and it gives a definition

SD = is the square root of its variance

and:-

variance of a random variable or distribution is the expectation, or mean, of the deviation squared of that variable from its expected value or mean.

OK.......so I can understand how to calculate it however.... I don't understand *why* you would want to calculate that?

Why not take the cube root of the variance, or 1/variance or log(variance) or sin(variance)

or indeed any other function you can think of???

I just do not see what is significant about the square root of the variance!!

Hope this is not a 'stupid question' :)