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# Edexcel S1 - 15th June, 2016 [Exam Discussion] watch

1. (Original post by hogree)
If you have a = 10x + 6 and b = 5x + 3

Saa = (10)(10)(Sxx)
Sab = (10)(5)(Sxy)
Sbb = (5)(5)(Syy)
what about when coding involves division
2. (Original post by not_lucas1)
whats the formula for them? I believe independent is comparing p(a)*p(b) with p(a intersect b) am i right?
Yup, it's at the end of Chapter 5 I believe. Mutually exclusive, intersection = 0
3. (Original post by hogree)
I cannot claim I am 100% certain. But I have seen a couple of people say this. Is there an example Question anywhere?That's exactly right. An example of this being used in Question 2 of Jan 2008.

I think that is right. Could I have a look at the example?
Cheers man, get it now haha

Scary how I can do C4 integration but can't do GCSE level maths
4. (Original post by hogree)
Yup it works. That's definitely the way to Code Regression. Fab
I fail to see how Q2 was an example of coding with Sxx, Sxy, Syy etc, I literally thought all you had to sub in the values for x and y
5. Division is just multiplying by a fraction, so the squaring still applies.
(Original post by QuantumStuff)
what about when coding involves division
6. https://1a388b28f5ce9318f837a64962fc...%20Edexcel.pdf

how would I do 5c?
7. (Original post by QuantumStuff)
what about when coding involves division
a = (x+6)/25 b = y/10 + 98

Saa = (1/25)(1/25)Sxx
Sab = (1/10)(1/25)Sxy
Sbb = (1/10)(1/10)Syy
(Original post by Mina_)
I fail to see how Q2 was an example of coding with Sxx, Sxy, Syy etc, I literally thought all you had to sub in the values for x and y
Yeah, it wasnt an example of coding with Sxx, Sxy, Syy - but you could have used that method if you had wanted to.
8. when does coding affect and not affect the answer? I cant remember what this is for but i remember it has/doesn't have an effect on something. I think it doesnt effect standard deviation or is it something else like pmcc?
9. (Original post by hogree)
If you have a = 10x + 6 and b = 5x + 3

Saa = (10)(10)(Sxx)
Sab = (10)(5)(Sxy)
Sbb = (5)(5)(Syy)
I thought coding didnt effect Syy ?!! Agh
10. (Original post by not_lucas1)
when does coding affect and not affect the answer? I cant remember what this is for but i remember it has/doesn't have an effect on something. I think it doesnt effect standard deviation or is it something else?
The key thing it doesn't affect is PMCC
Depending on the coding, other things may not be affected.
11. (Original post by Mina_)
I thought coding didnt effect Syy ?!! Agh
It only DOESNT affect Syy when there is no coding for Syy.

Coding X doesn't affect Syy.
Coding X and Y affects Syy.

EDIT: Sorry, I think I might have confused you by my coding. I didn't mean "b = 5x + 3", I meant "b = 5y + 3". So you're coding y, and that's why Syy changes.
12. (Original post by not_lucas1)
whats the formula for them? I believe independent is comparing p(a)*p(b) with p(a intersect b) am i right?
For independent you can either use:
P(AnB)=P(A)*P(B)
Or P(B)=P(BIA)
Or P(A)=P(AIB)

Mutually exclusive is just P(AnB)=0

Another one to remember is
P(AIB)=P(AnB)/P(B)
13. (Original post by hogree)
a = (x+6)/25 b = y/10 + 98

Saa = (1/25)(1/25)Sxx
Sab = (1/10)(1/25)Sxy
Sbb = (1/10)(1/10)Syy
Yeah, it wasnt an example of coding with Sxx, Sxy, Syy - but you could have used that method if you had wanted to.
so what is it was

a = (3x + 5)/7 b = (4x - 3)/2
14. Jan 15 ial

AN EXAMPLE OF CODING

A ninth year is added to the data set. In this year the price of the bottle of milk
is 46 pence and the price of a loaf of bread is 175 pence.
(e) Without further calculation, state whether the value of the product moment correlation
coefficient will increase, decrease or stay the same when all nine years are used.
15. Haven't had enough time to revise this, i messed up my revision schedule spending the majority of my time on physics and computing which dont even count this year... :/
16. (Original post by tazza ma razza)
Jan 15 ial

AN EXAMPLE OF CODING

A ninth year is added to the data set. In this year the price of the bottle of milk
is 46 pence and the price of a loaf of bread is 175 pence.
(e) Without further calculation, state whether the value of the product moment correlation
coefficient will increase, decrease or stay the same when all nine years are used.
will it stay the same because coding doesnt have an effect on pmcc?
17. In discrete random variables if it asks for F(3.5) and the X is between 3 and 4. Which would you use
18. Does anyone have any predictions on what will come up.. Like a hard probability question or something?
19. (Original post by not_lucas1)
will it stay the same because coding doesnt have an effect on pmcc?
That question is not actually coding, that's adding a new value to the Data Set. Since it is further from the Regression Line, the PMCC Decreases.
20. (Original post by not_lucas1)
will it stay the same because coding doesnt have an effect on pmcc?
This question is not on coding!

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