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

1. (Original post by Grecaj321)
How is e(r) o.45
I thought it was coding ??
As you did previously for x, but using 1/x in its place with the same probabilities.
I got r = -0.753 because I used the calculator value of Syy (716 with decimals) and not the given value of Syy (716 to 3sf)

Will I lose marks? Did anyone else get that?
Assuming it's the correct value, you won't lose marks. If the rounded and non-rounded values produce different answers, the mark scheme should allow a range that accommodates both.
3. (Original post by Mia66)
Just a quick question guys, I do As maths and fm, if I did badly in s1 and good in m1 would s1 be moved to fm and m1 be moved to maths?
.
The exam board will arrange your applied units to give you the best scores in both. For example, if you got an A in M1, B in S1 and A in D1, accompanied by two strong As in C1 and C2 and perhaps a B in FP1; they will put the B for S1 with C1 and C2 to still give you an A, thus leaving the As to go with FP1 forming your FM grade.
4. (Original post by Nikhilm)
Lmaolol my wiggle comment got 6 likes yours got one get wrecked
Srs? Are you going to snap a picture of your nether regions and compare it too?

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5. Can anyone remember the value of Sxy in one of the questions? It gave you the sum of X y and the sum of X I think?

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6. (Original post by SelfishWeiner)
Assuming it's the correct value, you won't lose marks. If the rounded and non-rounded values produce different answers, the mark scheme should allow a range that accommodates both.
But how do I know its right?

So I got Syy = 716 with a load of decimals after then rounded to 3sf like they asked.

Then when calculating r I plugged my value that had decimals

So I got Syy = 716 when it was rounded to 3sf does that mean its correct?
But how do I know its right?

So I got Syy = 716 with a load of decimals after then rounded to 3sf like they asked.

Then when calculating r I plugged my value that had decimals

So I got Syy = 716 when it was rounded to 3sf how do I know if its right or not
As long as you used the correct method and it is clear you got 716 when rounded you will get the marks I think.
8. (Original post by pranto96)
SD will not change! SD is root of sum of X - X bar divided by n. So as X- X bar is O is this case so sum of X-X bar do not change! so SD remains the same!
Not sure if you've already had a reply to this but 'n' is the total number of values and if you include another value n increases meaning X-Xbar over n decreases.
9. I dropped around 8 marks, would that be 90 UMS?
10. (Original post by CrazyFool229)
As long as you used the correct method and it is clear you got 716 when rounded you will get the marks I think.
Okay thanks
11. (Original post by iMacJack)
Can anyone remember the value of Sxy in one of the questions? It gave you the sum of X y and the sum of X I think?

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12. (Original post by SelfishWeiner)
Assuming it's the correct value, you won't lose marks. If the rounded and non-rounded values produce different answers, the mark scheme should allow a range that accommodates both.
Can you clarify how to calculate E(R)?
13. (Original post by Lucymariexoxo)
.
The exam board will arrange your applied units to give you the best scores in both. For example, if you got an A in M1, B in S1 and A in D1, accompanied by two strong As in C1 and C2 and perhaps a B in FP1; they will put the B for S1 with C1 and C2 to still give you an A, thus leaving the As to go with FP1 forming your FM grade.
that's so good to hear! I was just worried that the exam board will prioritise maths and place the module with the highest ums in maths
14. What would 201/225 be in UMS???

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15. i think i rounded one of the pmcc answers to 2dp . so 0.75 does anyone know if i would still get a mark ? as on the markschemes its usually to three or more dp
16. Yeah, you had to work backwards, so sd^2 + mean^2 = sum of fy^2 / sum of f ,
multiply 'sd^2 + mean^2' by sum of f , giving you sum of y^2
then to get y (as opposed to the mean) multiply the mean on y by the frequency (I think it was like 58x8)
then put those in your Syy equation : sum(y^2) - (58x8)^2/8

I don't remember the answer, but thats what I did :P
Seemed like a lot of working for just one mark ...
17. (Original post by LukeB98)
Nope, the mean stayed the same. If you add something that is the mean, it's going to stay the same. Checking on the calculator only confirms the assumption.

The standard deviation does, however change. I believe it decreases as you are reducing the spread of data in this circumstance.
This is a maximum concurrence. Thank you.
18. (Original post by Dark knight123)
basically guys for the diner question i got 17 people, is this correct and if not what was it and why?
cheers

I got 17 aswell but I'm not sure if its right
19. (Original post by neyjunior)
Can you clarify how to calculate E(R)?
R= 1/X

Hence E(R)=

(1/(-2) * 0.175)+(1/(-1) * 0.15)... + (1/(2) * 0.175)
Basically take 1 over the values when calculating E(X) and multiply by the probability for each. Hope this helps
20. (Original post by Tomilolaa)
Yeah, you had to work backwards, so sd^2 + mean^2 = sum of fy^2 / sum of f ,
multiply 'sd^2 + mean^2' by sum of f , giving you sum of y^2
then to get y (as opposed to the mean) multiply the mean on y by the frequency (I think it was like 58x8)
then put those in your Syy equation : sum(y^2) - (58x8)^2/8

I don't remember the answer, but thats what I did :P
Seemed like a lot of working for just one mark ...
Haha yeah I did that method too. Does seem harsh for 1 mark when I have seen questions like that worth 3 marks on the Solomon papers.

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