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

1. (Original post by wenogk)
I really don't get that, can you tell me what the class width is - is it 5 because its in the 5< y <10 class... Would you be kind enough to do this question plsss
Your 18.26 is the mean +1 standard deviation. You are asked to see how many plants are bigger than this. So you need to see how many plants are in the 15 to 25 interval are bigger than 18.26.
You need to know how many plants are bigger than 18.26 in this interval.
So find the fraction of the interval you have which is 3.26/10 (how far along the interval you are/ the interval size)
Multiply this fraction by 12 to see how many plants this is (3.91)
So the plants in the interval bigger than this is (12-3.91) = 8.09
Add the 4 plants in the higher interval is 12.09 (=12)
hope this helps
2. (Original post by Glib)
Any really hard papers?
Jan 2016 IAL and june 2015 .
3. (Original post by Person18)
As long as you didn't cross it out, you'd get the marks
so if i am unsure of a question i can potentially answer it more than once as long as i don't cross out?
Jan 2016 IAL and june 2015 .
where can i find jan 2016 ial?
5. (Original post by haes)
where can i find jan 2016 ial?
I can only find it but with an unofficial mark scheme attached (on tsr). Jan 2015 IAL looks hard also(its on physicsandmathstutor).
6. (Original post by haes)
where can i find jan 2016 ial?
Someone posted in on the thread here: http://www.thestudentroom.co.uk/show...&postcount=266
7. (Original post by hogree)
Someone posted in on the thread here: http://www.thestudentroom.co.uk/show...&postcount=266
thank you!
8. (Original post by candol)
Your 18.26 is the mean +1 standard deviation. You are asked to see how many plants are bigger than this. So you need to see how many plants are in the 15 to 25 interval are bigger than 18.26.
You need to know how many plants are bigger than 18.26 in this interval.
So find the fraction of the interval you have which is 3.26/10 (how far along the interval you are/ the interval size)
Multiply this fraction by 12 to see how many plants this is (3.91)
So the plants in the interval bigger than this is (12-3.91) = 8.09
Add the 4 plants in the higher interval is 12.09 (=12)
hope this helps
Wow thank you so much!
9. (Original post by 4nonymous)
Here's how I did it:
1 standard deviation above the mean has a yield of 18.3 so you need to look at the group 15<y<25
So for normal interpolation you do
Lower bound + how far in group/frequency of group *class width =18.3
and so rearrange to get how far in the group=18.3 - LB /class width *frequency

So
15 + ?/12 * 10=18.3
rearrange ?=3.96
But this shows the number of plants that have a yield between 15<y<18.3
and you want above so in that group there are 12 plants so 12 - 3.96 + the extra 4 in the next group =12.04 so 12 plants.
Yay I got it, you guys rock!
10. When they say give an interpretation of b ,what is usually meant ?
11. Just found some notes I made a long time ago, and I don't recognise this equation from any past papers. Is there any chance that it could come up?

"Discrete uniform distribution: Var(X) = (n+1)(n-1)/12 = (n^2 - 1)/12."
12. (Original post by ombtom)
Just found some notes I made a long time ago, and I don't recognise this equation from any past papers. Is there any chance that it could come up?

"Discrete uniform distribution: Var(X) = (n+1)(n-1)/12 = (n^2 - 1)/12."
I have not come across it in past papers.I remember asking my teacher and she said it was unlikely.I think you just need to recognise a discrete uniform distribution and know the EX value is the middle number by symmetry.
13. (Original post by Florent venhari)

How do you do question 1 in this paper. I can't really picture how the tree diagram would look like
https://0120b046f61e7ee5f95eb1315051...%20Edexcel.pdf

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When they say give an interpretation of b ,what is usually meant ?
Jan 2016 IAL and june 2015 .
do u have a link for Jan 2016 IAL? thanks
16. (Original post by lydiaws)
do u have a link for Jan 2016 IAL? thanks
Look a couple of comments above on this same page ,hoegree gave an excellent link.
17. Anyone have notes on the answering the worded questions about benifets of stat models e.t.c.

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18. fml
19. (Original post by hogree)
Is there a particular question that you find hard? One thing to remember that PMCC never changes with coding. Dont know if this helps?

Nope. Tree Diagrams arent always independent. So flipping a coin would be an independent event, since the second flip doesn't change dependent on the first flip. But boys and girls cycling to school would be dependent as the odds for cycling would go up, say, if you were a girl in comparison to if you were a boy.
Because women can't drive???😏😏😂
Kiddddingggggg.
Anywayssss. Thanks that makes sense actually )
20. Yo guys, do we have to learn all the proofing for all the equations in S1, if so, anyones got all the proofs?

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