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# S1 - Standard Deviation watch

1. Hi there,

there's this formula right?:

Now, there was someone asking the question, would the sigma f cancel each other out, top and bottom...

Now I know this can not work, because then the formula wouldn't make any sense but then on the other hand, there is nothing that can be said against it, everything is multiplied so you can easily cancel out?

cheers
2. (Original post by StylaBoy)
Hi there,

there's this formula right?:

Now, there was someone asking the question, would the sigma f cancel each other out, top and bottom...

Now I know this can not work, because then the formula wouldn't make any sense but then on the other hand, there is nothing that can be said against it, everything is multiplied so you can easily cancel out?

cheers
It's square rooted, so you can't.
3. There are two reasons why this is wrong and neither is because it is square rooted.

1) The top could technically read sigma(f(x-x bar)squared) (sorry about the lack of clarity here)

2) sigma is an operation not a quantity - it a bit like f(x)/f(y) - you don't cancel to get x/y do you.

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