The Student Room Group

OCR (not MEI) S2 - 22/06/2011

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Reply 60
Original post by Xero Xenith
As requested, my answers :smile: note I may have made mistakes!

(stored on calc in exam)

2. 57.4
3. 0.0473
4ii. 2.4
5i. 0.0464 reject H0
6i. 0.0156 accept H0
7i. n=15
7ii. 0.1635
7iii. 0.2287
8bi. 0.516
8bii. 0.0337


Did the same :P Got 0.471 for 3, but that could have been using calculator rather than tables....
Original post by Fstream
What do you think the grade boundary for an A? I found it rather easy, though screwed up completely q.3 worth 7 marks. I know a few answers if people want :P


Answers? Please do :smile:
Original post by will1992
Ooo interesting exactly the same as me i believe apart from 8biii (but i was a bit dubious so who knows)


I checked my answer to bii using the result from biii (which had no numbers in it except e).
Reply 62
1. u=52.5, sigma=3. Although you probably didn't post that one as it was the easiest o.O

Was q.6 the one on daily temperature?
Reply 63
Original post by Fstream
1. u=52.5, sigma=3. Although you probably didn't post that one as it was the easiest o.O

Was q.6 the one on daily temperature?


6 was the 11 marker on temp yeah - does anyone have their value of s^2 and distribution - i accepted it but wondering if i did so correctly - i had ~N(24.3,0.845) - (cant remember if that was x or x bar
Reply 64
Could someone remind me what questions 3 and 4 were about? I can't remember my answers to those but apart from that i got exactly the same :smile:
Reply 65
Original post by phil_1993
Could someone remind me what questions 3 and 4 were about? I can't remember my answers to those but apart from that i got exactly the same :smile:


3 was the type II error hyp test (i think) - 4 was sketch f(x) and find variance (i think)
Reply 66
Original post by will1992
3 was the type II error hyp test (i think) - 4 was sketch f(x) and find variance (i think)


Cheers that helps - i think i left 4 as 12/5 which is why it didn't sound familiar
Reply 67
I can't remember my answersz
..though some do sound familiar..
Does anyone remember their rejection region for 5i)..
Okay that wasn't TOO bad. Most people at my college didnt get the Type 2 error question correct (including myself!), so that could bring the boundary down.

For the last question, last part...the question said

in the general case, show algerbraically that:
P(R=0 and S=1) + P(R=1 and S=0) = P (T=1)

I stupidly wrote that as:

e^-2 * 3e^-3 + 2e^-2 * e^-3 = 5e-5 = RHS

I didnt GENERALISE it. how many marks will I lose?
Original post by natashabedford
Okay that wasn't TOO bad. Most people at my college didnt get the Type 2 error question correct (including myself!), so that could bring the boundary down.

For the last question, last part...the question said

in the general case, show algerbraically that:
P(R=0 and S=1) + P(R=1 and S=0) = P (T=1)

I stupidly wrote that as:

e^-2 * 3e^-3 + 2e^-2 * e^-3 = 5e-5 = RHS

I didnt GENERALISE it. how many marks will I lose?


Many people did this. 2-3?
Original post by Xero Xenith
Many people did this. 2-3?


Ok, do you mean 2-3/4 correct or i will get 2 or 3 marks deducted?

Thanks :biggrin:

also what do you think 90 and 100 UMS will be for this paper?
a lot of people seem to have found this easy, including me. when i walked out of the exam hall, i didn't feel too bad, not worse than my core 3 or core 4 exam anyway. although, this is a worrying sign to me that the grade boundaries will be high.
Reply 72
What were questions 7ii to 8bi?
Reply 73
Won't Mr M post the answers up?

I was hoping I'd see if any answers are familiar then just crash.
Reply 74
Original post by Jodin
What were questions 7ii to 8bi?


Was 7 the poisson distribution Q? Something about probability for 40 weeks being something 7. 8 was like 1 mark and 2 mark Q at first, cant remember the Q :s-smilie:
Then something about R=0 (R is that lambda sign, S is the mu sign, T is lamba + Mu [excuse my math spellings]). I have no idea; something along these lines maybe these will trigger ur thoughts.
Reply 75
Original post by Twinkles
Was 7 the poisson distribution Q? Something about probability for 40 weeks being something 7. 8 was like 1 mark and 2 mark Q at first, cant remember the Q :s-smilie:
Then something about R=0 (R is that lambda sign, S is the mu sign, T is lamba + Mu [excuse my math spellings]). I have no idea; something along these lines maybe these will trigger ur thoughts.


No I remember it roughly though, IIRC the 8b ii was like lambda = 2.73 so probability of greater than 2 = 1- (e^-(2.73)(1 + 2.73)). The one of the 8 part ii was treating it as a normal with N(44,44) and the other was considering it as a binomial and then a normal to get (5.74, some other stuff), ring any bells?
Okay that wasn't TOO bad. Most people at my college didnt get the Type 2 error question correct (including myself!), so that could bring the boundary down.

For the last question, last part...the question said

in the general case, show algerbraically that:
P(R=0 and S=1) + P(R=1 and S=0) = P (T=1)

I stupidly wrote that as:

e^-2 * 3e^-3 + 2e^-2 * e^-3 = 5e-5 = RHS

I didnt GENERALISE it. how many marks will I lose? anyone plz
Reply 77
Original post by Jodin
No I remember it roughly though, IIRC the 8b ii was like lambda = 2.73 so probability of greater than 2 = 1- (e^-(2.73)(1 + 2.73)). The one of the 8 part ii was treating it as a normal with N(44,44) and the other was considering it as a binomial and then a normal to get (5.74, some other stuff), ring any bells?


The one's youve describe sound familiar but werent they question 7? :tongue: i only finished this a hour ago and cant remmeber the question order :P
Reply 78
Original post by natashabedford
Okay that wasn't TOO bad. Most people at my college didnt get the Type 2 error question correct (including myself!), so that could bring the boundary down.

For the last question, last part...the question said

in the general case, show algerbraically that:
P(R=0 and S=1) + P(R=1 and S=0) = P (T=1)

I stupidly wrote that as:

e^-2 * 3e^-3 + 2e^-2 * e^-3 = 5e-5 = RHS

I didnt GENERALISE it. how many marks will I lose? anyone plz


It was worth 3 marks but it did say in the question give a algebraic proof or something so prehaps 1 or 2. Unless it was purely there to catch people out i wouldnt have thought theyd take all the marks away.
Original post by mrppaulo
It was worth 3 marks but it did say in the question give a algebraic proof or something so prehaps 1 or 2. Unless it was purely there to catch people out i wouldnt have thought theyd take all the marks away.


It was actually worth 4 :\

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