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

1. (Original post by sgill23)
is like a solid 4 full days enough to cover stats, hoping for an A any suggestions of what to do?
Watch the exam Solutions S1 vids and the Hegarty Maths ones if you still need more work on some topics. Learn it all in 2 days max and then start doing exam papers. But once you've learnt a topic then do some exam questions on that topic to consolidate it.

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2. (Original post by aj2152)
Watch the exam Solutions S1 vids and the Hegarty Maths ones if you still need more work on some topics. Learn it all in 2 days max and then start doing exam papers. But once you've learnt a topic then do some exam questions on that topic to consolidate it.

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thank you!!
3. Need a bit of help with Q7, January 2011. Part b.
I don't understand how you know to do what it says in the mark scheme. I calculated each part of the tree diagram and then added together the values that start with the two same colours. This is incorrect apparently and I dont understand why
EDIT: Sorry ignore me. I can't use my calculator apparently. The way i did it is correct too
4. I am really confused by this mark scheme for question 6 part b.
https://1a388b28f5ce9318f837a64962fc...%20Edexcel.pdf

It says you get a b1 mark for +-((s-162)/7.5)=0.2553

but if you solve that with the minus you get:
-0.2553=((s-162)/7.5)
s=160.08525

but then in the final a1 mark, you only get the mark for answers which round to 184 which is what happens when you solve it with the positive?

why
5. (Original post by KloppOClock)
I am really confused by this mark scheme for question 6 part b.
https://1a388b28f5ce9318f837a64962fc...%20Edexcel.pdf

It says you get a b1 mark for +-((s-162)/7.5)=0.2553

but if you solve that with the minus you get:
-0.2553=((s-162)/7.5)
s=160.08525

but then in the final a1 mark, you only get the mark for answers which round to 184 which is what happens when you solve it with the positive?

why
Well we know that the mean is 162, therefore the value of the 160.08525 goes against the idea that its in the 60th percentile. The value of 163.9 is correct. The reason you need the +- is to show that there IS a possible second value, but the question says Sarah remains in the 60th percentile.
6. Is it just me or are the R papers really difficult? Like everything else I can do but the R papers are just so easy to lose marks with
7. (Original post by studentsixth)
Is it just me or are the R papers really difficult? Like everything else I can do but the R papers are just so easy to lose marks with
Well... They ARE REPLACEMENT papers! They're designed quite horribly if you ask me, some years they've been built well, but most of the time the boards just throw them together. They are not nice, no where, but if you can do those well and Solomon papers (obviously do the normal papers too) and you have a sound understanding of the topics, you'll be sorted!
8. (Original post by mahesh114)
Well we know that the mean is 162, therefore the value of the 160.08525 goes against the idea that its in the 60th percentile. The value of 163.9 is correct. The reason you need the +- is to show that there IS a possible second value, but the question says Sarah remains in the 60th percentile.
ah okay, i just didnt know what percentile meant. thanks
9. Can anyone show me a step by step by solution for part c)

On a randomly chosen day the probability that Bill travels to school by car, bicycle or on foot is 1/2, 1/6, 1/3 respectively. The probability of being late when using these methods of travel is 1/5, 2/5, 1/10 respectively.
a) draw a tree diagram to represent this information
b) find the probability that on a randomly chosenday
i) Bill travels by foot and is late
Ii) Bill is not late
C) given that Bill is late, find the probability that he did not travel on foot.

I have done a and b and for c i have got this far
P (F'/L)
P (F' and L) / P (L)
P (F' and L) / 1/5

Im confused on how to solve thr numerator on a tree diagram.
10. Hey can someone tell me when i need to do (n+1)/2 and when to do n/2 to find the mean for linear interpolation??????
11. (Original post by sgill23)
thank you!!
I recommend you watch KESMaths S1 videos - they are by far the best S1 videos on YouTube
12. For part c I don't understand why you pick P(L>133) instead of P(L<133).

13. Hey guys can anyone explain to me the First part. I am just confuse with when I have to write in prabability or whole number. I usually write opposite, but it is not required.
14. (Original post by KloppOClock)
ah okay, i just didnt know what percentile meant. thanks
You just find the z value for the people 'above' her for this type of question- i.e. 40% which gives a z value of 0.2533 - then you can find your height from there, which I presume you know how to do.
15. (Original post by mahesh114)
Well... They ARE REPLACEMENT papers! They're designed quite horribly if you ask me, some years they've been built well, but most of the time the boards just throw them together. They are not nice, no where, but if you can do those well and Solomon papers (obviously do the normal papers too) and you have a sound understanding of the topics, you'll be sorted!
They're the regional papers, to accommodate for different time zones.
16. (Original post by Marxist)
You just find the z value for the people 'above' her for this type of question- i.e. 40% which gives a z value of 0.2533 - then you can find your height from there, which I presume you know how to do.
yh i knew how to do it, i just worked out the probably for the 40th percentile which at the time i thought was the 60th percentile
17. (Original post by target21859)
For part c I don't understand why you pick P(L>133) instead of P(L<133).
Well you already know that the question is asking what the probability of her phone lasting 133 hours is. Think about it this way....

P(not need charging after 133 hours)
= P(L>133 | L>127)
= _P(L>133)_
P(L>127)

^It's probability after 133 hours because why would she want to charge her phone before her flight is over!

Hope this helps
18. 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
19. (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
Yeah I believe so
20. (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
Correct

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