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# S2 Edexcel Thursday 24th May AM - PAPER & SOLUTIONS IN FIRST POST Watch

1. (Original post by maths134)
right two questions, are you allowed to integrate between 2.5-1.5 and take it away from one? its just because you didnt do it that way. Also with the hypothesis test where we would poisson/binomial, i listed both hypotheses, one with lambda, one with 'p' is this correct? If this is fine then i got 100
Yes both are correct.
2. For the last question I did X-N(30, sqrt12squared)

(n-30)/sqrt12 = 1.29 (from z tables)
so n-30 = 4.47
so n = 34.47
so n =35

Gibbo, do you think I'll get the marks???

Edit ; I forgot the squared after the squareroot of 12!! (I did remember it in the exam)
3. (Original post by usamakhanlodhi)
Hopefully.. I didnt even think of that so much wasted time
So how did u do in this paper, and what do u need?
It seems I did okay, although I usually tend to make silly mistakes on easy questions :P
The higher the better! Means less pressure on other modules!
4. (Original post by mld)
For the last question I did X-N(30, sqrt12)

(n-30)/sqrt12 = 1.29 (from z tables)
so n-30 = 4.47
so n = 34.47
so n =35

Gibbo, do you think I'll get the marks???
You mean X~N(30,12), right? It was only a three mark question so you may get the marks, but I'm not sure. An examiner/teacher would have a better idea if there are any around...
5. (Original post by OneMorePanda)
How did you lot do "Write down E(X)."?

I had to use integration, which probably wasn't the way they wanted.
It was symmetrical! So you could just use middle x value.
6. Oh no. I think I might have messed up the second to last question too... Where the answer included 0.0464. I remember that value, but I think I crossed it out!
67 won't drop below an A will it? I need an A in this to get to university.
7. Would I get any marks if on Question 8 part a) I used poisson x~Po(6) instead of binomial?
It was symmetrical! So you could just use middle x value.
But some of us were so stressed out we didn't see that it was symmetrical so we integrated instead, and took half a page of working to get our mark
9. (Original post by mld)
But some of us were so stressed out we didn't see that it was symmetrical so we integrated instead, and took half a page of working to get our mark
I was so stressed at the prospect of doing a crazy integral, and thought there must be an easier way... PLEASE BE AN EASIER WAY! :P
I was so stressed at the prospect of doing a crazy integral, and thought there must be an easier way... PLEASE BE AN EASIER WAY! :P
You were right, it was symmetrical and I should have seen it. I will be teaching this module next year (aarrgghh), so I hope I pass with a good grade
11. Damn, that last question definitely threw me a bit. Got 34 instead of 35 think I got confused with my strict inequalities.
12. for last question both Poisson and Binomial are completely justifiable as all three criteria are met for both and they get different answers for all parts of the question B gets n=35 P gets it as 38. They may well allow either in the final mark scheme
13. (Original post by Gibbo81)
Yeah will be fine.
I guess you must have used the other distribution (50,0.4) ?
Yes i.e. P(X<35) = P(X<=34) = P(Y>= 16) which is greater than 0.9 etc. Thanks again! Also, just letting you know, your EDIT for Q2 is slightly wrong: it should be 0.0216 for that critical region .
14. How many marks would I lose for just finding the sampling distribution but not of the range?
15. (Original post by sweetascandy)
i got 16 but mine was wrong 2 other people I know got 35. I didn't even think to use the normal approximation. But I think it was only 3 marks. What did you get? And how did you find it overall??

BTW, when are the answers being posted??
I know exactly what you did because I got 16 and then 17. We're such fails but I'm feeling alright because I got everything else right .
16. Pretty sure I got between 70-72 marks.
17. u know q2 isn't the second critical 0.0216 not 0.0215

(Original post by Gibbo81)
Here are the solutions. Thanks for all the negative rep! I know Arsey is an insomniac but some of us need our beauty sleep!

It comes in two parts unfortunately (I just couldn't get it to less than 1MB).

I thought it was pretty easy with a couple of unusual questions so my best guess for grade boundaries is about 63 for an A.

Let me know what you think.

EDIT the value associated with the crit region in Q2 should be 0.0214 not 0.0215 (doing it in my head!)
18. (Original post by hudhud123)
u know q2 isn't the second critical 0.0216 not 0.0215

Thta's pretty much what I got as well 0.0216 for both tails....
19. I'm pretty sure I did awful.
I messed up from question 6 onwards... -Sob-
20. (Original post by Jullith)
I'm pretty sure I did awful.
I messed up from question 6 onwards... -Sob-
I got every 3 mark question wrong well I think I did, I may get method marks though

Updated: January 17, 2013
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