You are Here: Home >< Maths

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

Announcements Posted on
Why bother with a post grad? Are they even worth it? Have your say! 26-10-2016
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

Updated: June 11, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### Who is getting a uni offer this half term?

Find out which unis are hot off the mark here

Poll
Useful resources

## Make your revision easier

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

Can you help? Study help unanswered threads

## Groups associated with this forum:

View associated groups
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.