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# s2 OCR how did u find it?? watch

1. Yea I proved it. It was something like P(x>50) then continuity correction meant it was P(X>=50.5) i cant find greater than or equals to sign. stupid continuity corrections!!! i couldnt quite remember how to do it in exam tho so i did it lots of different ways until i got the right answer!
2. (Original post by starcrossed)
yeh i proved that, i no all 3 types of approxs were iin the paper, wat other qs was hard, could everyone prve the long eqn, t4 + ............... etc
Yeah you had to integrate between t0 and 0 to equal 0.95. then times by the fraction, then by 4 and you should get the same.
3. (Original post by Bhaal85)
I actually worked out the X values for which the regions would be rejected. I know that it was definitely two tailed. Thereofre you should have 2.5% at either end.
Thanks, that's what I did. I made a stupid mistake on question 2 and numbered the names 1-10, then got really confused. Maybe they'll got me a mark because they pity me.
4. i had the 0.918 for the X~p(7) thought it was to big so i crossed it out and did it using P(X<=3)...good bye 3 marks
5. (Original post by Bhaal85)
Yeah you had to integrate between t0 and 0 to equal 0.95. then times by the fraction, then by 4 and you should get the same.

i did all of that, except i didn't times by 4, lol i times by 250000 or something massive like that to get the same equation....
6. (Original post by Bhaal85)
There was a hell of a lot of continutity(sp) corrections!!! anyone else prove that 0.231 thing?

Yeah, I managed to prove it in the end. First time I forgot the cc, the next time I used the wrong one, then I finally got it right. Wasted a lot of time on that question.
7. All together it seemed a pretty good paper, not like all the higher pure modules, there didnt seem to be anywhere you could bin a load of marks, maybe just a few small things here and there. What do you reckon the grade boundaries will be like? Because i need a high UMS mark in this to get the grades for my oxford offer
8. (Original post by abc123)
i did all of that, except i didn't times by 4, lol i times by 250000 or something massive like that to get the same equation....
You should have taken out the multiplied the 0.95 by 62500, then the entire equation by 4.
9. (Original post by sock)
Thanks, that's what I did. I made a stupid mistake on question 2 and numbered the names 1-10, then got really confused. Maybe they'll got me a mark because they pity me.
I labelled them from 1-10 too, but then realised that I should have done 0-9, so I changed it, lol. It threw me quite a bit that question, how did people answer it? As this is something we don't normally do. I mean, what the hell, tables of random numbers? People pay for this crap? How does it work? lol. I then proceeded to select the '2nd' number from each set, until I had five.
10. (Original post by Bhaal85)
You should have taken out the multiplied the 0.95 by 62500, then the entire equation by 4.
yeah i see what your saying....although i'm quite sure the way i did would probably be valid since it all followed ok and i got to the final equation fine....i just multiplied the fraction (1/6750 or something) into the quartic, and then multiplied both sides by 250000 to get the right equation.
11. (Original post by Bhaal85)
I labelled them from 1-10 too, but then realised that I should have done 0-9, so I changed it, lol. It threw me quite a bit that question, how did people answer it? As this is something we don't normally do. I mean, what the hell, tables of random numbers? People pay for this crap? How does it work? lol. I then proceeded to select the '2nd' number from each set, until I had five.
I remember there being a question a bit like that in the mock exams in the textbook. I didn't understand it, so I asked a teacher about it, and he said chances are we wouldn't get a question like that, lol. Now I'm kicking myself for not asking him how to do it. Oh well, it's only 4 marks. Anyone else do M2 as well? What a fun afternoon that was, lol.
12. Oh well, THANK GOD for method marks!!!! lol. Anyway I really hope I get 90% plus.
13. I don't even know what a random no table is...I've never even heard of one before. I was so mighty confused when I got to that question. I just labeled each person with a number...in the order the numbers were given, then picked the first 5. tis about as wrong as you can get...but i figured doing something was better than nothign at all
14. Yeah, is that random number table stuff even on the syllabus, I've never seen it before, i just assigned each person with a range like 0 - 99 etc and then picked the first 5 numbers
15. yeah it is in the syllabus, its in the book somewhere in chapter 4 i think. its the bit with lots and lots of writing and u think, ill look at it later, and then dont. usually the question about number tables just come up in past papers about how u wud select a random sample, and u just vaguely mention it...not so this time
16. Well it was only 3 marks, and theres bound to be method marks in there somewhere, so whatever happened it cant be that bad
17. (Original post by starcrossed)
how did everyone do q6b, did u get lamde as 1.05 and then use the poisson formula to find x=0, x=1 x=2 and then do 1 minus that answer

I personally approximated them to a binomial distribution, with N 50 and P 0.021. Then did 1 - p(x = 1,2,3).
18. (Original post by pi is exactly 3)
Well it was only 3 marks, and theres bound to be method marks in there somewhere, so whatever happened it cant be that bad
to be honest i think the way you did it was correct anyway...its pretty simple when you think about it, its all about being confident witht the theory, even if its really simple...
19. (Original post by Bhaal85)
I labelled them from 1-10 too, but then realised that I should have done 0-9, so I changed it, lol. It threw me quite a bit that question, how did people answer it? As this is something we don't normally do. I mean, what the hell, tables of random numbers? People pay for this crap? How does it work? lol. I then proceeded to select the '2nd' number from each set, until I had five.
Label 1-10

Divide the numbers you are given by 100. Round them UP to the nearest whole integer. Ignore repeats.

Therefore 079 => 0.79 approx = 1 (Choose surname A)
831 => 8.31 approx = 9 (Choose surname I)

etc...
20. (Original post by Urdegish)
I personally approximated them to a binomial distribution, with N 50 and P 0.021. Then did 1 - p(x = 1,2,3).
I Used the binomial that way too, cant remember the answer though, was it something like 0.2 or 0.3?

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