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OCR MEI - S1 - 20th May 2015

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Original post by Ritesh Jethwa
Hi how u use the probability table for the hypothesis testing???


Also Ritesh
Original post by Mathbomb
Last answer is 1/57.
To get more than 2 he doesn't like before he gets one he likes he has to pick 3 cherries in a row.
This can be calculated by (6/20)*(5/19)*(4/18) or by 1 - (14/20) - (6/20)*(14/19) - (6/20)*(5/19)*(4/18).


It says he needs to make more than two picks, so if he picks cherry, cherry, apple (or w/ever flavour), that means he has made more than two picks, and finds one he likes.
what are the grade boundaries? like 56 for an A?
Original post by Setarehp
what are the grade boundaries? like 56 for an A?


It depends on how people found the paper and how many marks people got - if candidates, in general, got more marks than last year's students that sat last year's paper, the grade boundaries will go up to adjust for the change. If, in general, candidates got less marks than candidates did last year, the grade boundaries will go down to accommodate for that change. At the moment, it looks like it might be around 60-62 for an A.
Original post by Connorbwfc
You didn't use it in this exam because the specified probability of 0.78 isn't in the table.


No, you had to round to 0.8 and use the tables
Original post by Ritesh Jethwa
No, you had to round to 0.8 and use the tables

No.... you had to use the binomial distribution. I hope you're trolling.
where is aqa
These threads are dominated by the symonds mandem represent


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Original post by joe12345marc
S1 mark schemes are extremely annoying and horrible and I expect you to get 3/8 or if you also put "H1: p<0.78" then you'd get 2/8 :frown:


I did defining P, and the hypotheses right, so hopefully 3/8. This single handedly has caused me to scrape an A now :frown:
Original post by adrianblazesit
It depends on how people found the paper and how many marks people got - if candidates, in general, got more marks than last year's students that sat last year's paper, the grade boundaries will go up to adjust for the change. If, in general, candidates got less marks than candidates did last year, the grade boundaries will go down to accommodate for that change. At the moment, it looks like it might be around 60-62 for an A.


Thanks! what about a B?
For the Hypothesis Testing question conclusion, could you put "Accept H(o) because of insufficient evidence to prove that the new drug is more effective..." instead of "Reject H(1)"? Overall I think I only lost 6-8 marks in this exam even though I can't remember what I wrote I hope I didn't make any stupid mistakes like with C1...hoping for that high UMS so my S1 and C2 can help me get to an A! :smile:
Original post by Arkasia
It says he needs to make more than two picks, so if he picks cherry, cherry, apple (or w/ever flavour), that means he has made more than two picks, and finds one he likes.


If you look at it, both could evidently be right so clearly it was a super mean question. I saw it as you did, as he found e.g cherry then cherry then something else, but I actually think they may be right. Stupid stupid question, however nothing we can do. Because, some people use the word "before" for different uses, so genuinely some people think it means something else. And cos you know S1, we'll all lose all 4 marks for it.
Original post by Mathbomb
Last answer is 1/57.
To get more than 2 he doesn't like before he gets one he likes he has to pick 3 cherries in a row.
This can be calculated by (6/20)*(5/19)*(4/18) or by 1 - (14/20) - (6/20)*(14/19) - (6/20)*(5/19)*(4/18).


I answered the question this way, also. I agree with joe above - the way the question is worded it could be either way, and obviously in the exam I assumed it was this way. I've been thinking about it pretty much all day, and I still can't be 100% I've got my head around it. I'm pretty sure this is the only thing where I could have dropped (big) marks, so I'm alright either way.

Maybe OCR will realise they goofed with the wording and give marks equally to both answers lol.
Original post by Studious_Student
For the Hypothesis Testing question conclusion, could you put "Accept H(o) because of insufficient evidence to prove that the new drug is more effective..." instead of "Reject H(1)"? Overall I think I only lost 6-8 marks in this exam even though I can't remember what I wrote I hope I didn't make any stupid mistakes like with C1...hoping for that high UMS so my S1 and C2 can help me get to an A! :smile:


Yes, definitely. My teacher told us specifically to answer in terms of H0, because you haven't taken any steps to prove the validity of H1, so the only way you can answer with absolute certainty is with relation to H0.
Original post by Setarehp
Thanks! what about a B?


If 60-62 is an A, then a B is probably 53-55. However, I don't think boundaries are going to be that high this year - I'd say A is more likely to be around 58, and B respectively lower.
Original post by jpetersgill
These threads are dominated by the symonds mandem represent


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Big up psc
did anyone else find the rugby team question familiar? I'm pretty sure it cropped up in a past paper before but I don't know which one now
Is this right for the last question?

1 - [ (14/20 × 13/19 × 12/18) + (6/20 × 14/19 × 13/18) + (6/20 × 5/19 × 14/18) ]

= 0.459649123 = 0.4596 (4 sig figs)
P(x>2) = 1 - p(x<=2)
Original post by Duskstar
I answered the question this way, also. I agree with joe above - the way the question is worded it could be either way, and obviously in the exam I assumed it was this way. I've been thinking about it pretty much all day, and I still can't be 100% I've got my head around it. I'm pretty sure this is the only thing where I could have dropped (big) marks, so I'm alright either way.

Maybe OCR will realise they goofed with the wording and give marks equally to both answers lol.


Here's my two sense: Say he got Cherry Cherry Other - you could say "he had to take more than 2 before getting one he likes"
Then now say he got Cherry Cherry Cherry other - you could say "he had to take MORE THAN 2 BEFORE getting one he likes". Same phrase, different emphasis, so different meaning.

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