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

1. (Original post by Aliceeee12)
Hi guys! Does anyone know the answer to this?

Is the sd affected by multiplication or addition
Is the mean affected by multiplication or addition
sd is affected by only multiplication/division
mean is affected by multiplication, division, addition and subtraction

standard deviation measures how spread out data is from the mean.

logically, if you added 10 to each piece of data, the standard deviation would stay the same as each point would move 10 places and the distance between them would stay the same. so standard deviation is not affected by addition/subtraction. however, standard deviation IS affected by multiplication/division. Think of transforming graphs-- when you add or subtract 2 from a graph, all points move 2 places. if you multiplied a graph by 2, the graph is stretched and the distance between each point has changed. in the same way, standard deviation is affected by multiplication/division

as for the mean...it is a measure of location and is affected by ALL coding.
Does S1 have any annoying rules with rounding and significant figures like M1 does (in M1 every answer must be given to 2sf or 3sf).

Most mark schemes say "awrt", is this always the case?
Assuming they dont specify anything in the question, any number of decimal places/sig figs is always accepted?

do you know how coding affects Sxx, Sxy and Syy ?
I'm so confused
3. (Original post by siamesedaffodil)

do you know how coding affects Sxx, Sxy and Syy ?
I'm so confused

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4. thanks for that!

do you think Sxy and Syy would be decoded that way too?
5. (Original post by siamesedaffodil)

do you know how coding affects Sxx, Sxy and Syy ?
I'm so confused
Sxx, Sxy, Syy are only affected by multiplication/division and it is the factor squared. So similar to variance in that sense
6. Can someone explain (e) and (f) to me?
It's June 2015 IAL
http://imgh.us/Untitled_677.png
7. What exactly must you make sure you do when drawing a line of regression? Like should i extrapolate to the y axis, should i plot the mean points ??
8. Guys how many marks would i roughly need for full ums
9. (Original post by AmarPatel98)
What exactly must you make sure you do when drawing a line of regression? Like should i extrapolate to the y axis, should i plot the mean points ??
line of regression must pass through the mean point
10. Does anyone else think some of the questions where you have to answer in words are ********?
11. say if you don't do as well on one module but are not taking maths at A2 are you allowed to resit one of the modules or do you have to retake all of them
12. you would only be able to retake if you are carrying on with maths onto A2
13. (Original post by Electrify)
Can someone explain (e) and (f) to me?
It's June 2015 IAL
http://imgh.us/Untitled_677.png
can you send the link for the whole paper?
14. (Original post by Electrify)
Can someone explain (e) and (f) to me?
It's June 2015 IAL
http://imgh.us/Untitled_677.png
var(y)= K^2*var(X) and c is the value of y when k is zero
15. When new values are added to the data how do the mean/median/sd/PMCC/Sxx/Sxy change? Does it depend on the value that was added, and if so how?

e.g i just did question 2e here and i understand the first two but why does standard deviation decrease?
16. so deciles.....

would d1 mean 10% of the data, d6 mean 60% data, etc....?
17. apart from the gold papers, which paper is the hardest? also any particularly unique or difficulty questions anyone has come up against?
18. (Original post by Philip-flop)
Ok so this is a bit of a noob question about Venn diagrams but...

Are the shaded regions I've shown in the picture below the P(AnB)'
Click to enlarge
Attachment 547855
I like to think it says Probability of A "and" B. So yeah that is A and B
19. (Original post by KloppOClock)
apart from the gold papers, which paper is the hardest? also any particularly unique or difficulty questions anyone has come up against?
June 2010 has the lowest grade boundaries, I personally didn't like the 2009s
20. (Original post by physicsamor)
June 2010 has the lowest grade boundaries, I personally didn't like the 2009s
thanks ill try the 2009 ones now

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