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# The effect of coding on Sxx/Syy/Sxy? Watch

1. What is the effect of coding data on the values of Sxx, Sxy and Syy. I realise r just remains the same. This is for statistics S1
2. You're not getting much response - so I'll take a stab at this.

If you add a fixed amount to either the x or y values you will not affect any of Sxx Sxy or Syy because they all subtract the mean.

If you multiply the x values by say 2 you will quadruple the Sxx value, double the Sxy value and not change the Syy value.
3. (Original post by ian.slater)
You're not getting much response - so I'll take a stab at this.

If you add a fixed amount to either the x or y values you will not affect any of Sxx Sxy or Syy because they all subtract the mean.

If you multiply the x values by say 2 you will quadruple the Sxx value, double the Sxy value and not change the Syy value.
So it's like variance then; in saying that Var(2X+5)=22Var(X) in the case of Sxx and then for Sxy it's like standard deviation (presumably because the x value isn't squared in an Sxy calculation).

Thanks for responding
4. (Original post by the.austrian)
So it's like variance then; in saying that Var(2X+5)=22Var(X) in the case of Sxx and then for Sxy it's like standard deviation (presumably because the x value isn't squared in an Sxy calculation).

Thanks for responding
Yes, exactly the same, make sure you square it as you've said
5. So if you are multiplying x by 9, would Sxx be multiplied by 81??
6. (Original post by Ellieseftel)
So if you are multiplying x by 9, would Sxx be multiplied by 81??
You catch on fast

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