S2 Edexcel Thursday 24th May AM - PAPER &amp; SOLUTIONS IN FIRST POST

OP

Original post by racing_stripes

Hi, was just wondering about the grade boundaries as I think I've possibly got 63 from your marksheme but i know that an A can be as high as 69-70/75, do you think that 63 would be suitable for A considering the previous papers and woul;d you say this was a reasonable paper or quite a hard paper.

I thought it was quite easy until q6. There were just some unusual questions. Most people practice for these exams by caning past papers so when stuff comes up that hasn't been on any papers for a while (like q6) they get it wrong. Based on what people are saying it seems like a hard paper. I would say 63 is the max for an A.

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Reply 522

Gemxx

Hello! For the sampling distribution 6 MARKS one, I completely went blank!!
I wrote the mean of number of 1 is: (0.65)^3 + ((0.65)^2 x (0.35) x 3) = 0.71825
The mean of 2 is: 1 - 0.71825= 0.28175
I know I wrote nothing about range or doesn't even remotely look like the markscheme therefore does that mean I'll get 0/6 marks :frown:

... I think I'll just go off and cry!

Reply 523

master_blaster66

17

Original post by Gibbo81

I thought it was quite easy until q6. There were just some unusual questions. Most people practice for these exams by caning past papers so when stuff comes up that hasn't been on any papers for a while (like q6) they get it wrong. Based on what people are saying it seems like a hard paper. I would say 63 is the max for an A.

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for the Hypothesis Testing Q, if you converted the Binomial to Poisson before stating your hypotheses, and then gave Ho as Lambda = 6 and H1 as Lambda > 6...instead of p = 0.03 and p > 0.03...would you still get all marks for that?
thanks gibbo

Reply 524

OP

Original post by Gemxx

Hello! For the sampling distribution 6 MARKS one, I completely went blank!!
I wrote the mean of number of 1 is: (0.65)^3 + ((0.65)^2 x (0.35) x 3) = 0.71825
The mean of 2 is: 1 - 0.71825= 0.28175
I know I wrote nothing about range or doesn't even remotely look like the markscheme therefore does that mean I'll get 0/6 marks :frown:

... I think I'll just go off and cry!

Sorry but looks like 0!

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Reply 525

OP

Original post by semi-skimmed

Wow got nearly the same as Gibbo81 except i put 3 tables for question 6. I think i was just a weird paper tbh but thanks to gibbo's previous markschemes and stuff i'm just hoping i did enough to do well. Gibbo if i've done well your a legend! If not ... i blame my teacher

Sounds like a plan!

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Reply 526

exam2k10

Sorry Gibbo, but for some reason for the CDF question I got the constant for the 4<x<10 range as 16/15. My mates also got that.

Now I don't want to say your wrong or anything but how many marks would I lose for that error? Also will I lose 2 marks for the following question? :frown:

For the sampling distribution, I listed all the possibilites as well as their probabilites but then I didn't put it in a table format. How many marks would I get? 5/6?

Thanks

Reply 527

knowledgecorruptz

Original post by Gibbo81

Not sure. I'll have to look at some previous mark schemes. Don't think there's much wrong with what you've done.

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Awesome, I'd really appreciate that :smile:

I've had a look at the most recent papers but nothing like that comes up...so I dunno, should be okay though I reckon.

Also, with the Q asking about conditions for Binomial to be approximated with Poisson, I wrote out "n large", "p small", "np <= 10", "mean near variance", but then I also wrote "probability is constant", "singly", "independent". If they positively mark I'm guessing I wouldn't lose anything for that?

Cheers

Reply 528

IAmTheChosenOne

For the sampling distribution, do i need to write it up nicely/ mathematically? I just wrote "probability of being 0 = ........" etc
Will i get full marks?

Reply 529

bexlovescandy

Original post by IAmTheChosenOne

For the sampling distribution, do i need to write it up nicely/ mathematically? I just wrote "probability of being 0 = ........" etc
Will i get full marks?

I did a similar thing...I'm not sure

Reply 530

OP

Original post by exam2k10

Sorry Gibbo, but for some reason for the CDF question I got the constant for the 4<x<10 range as 16/15. My mates also got that.

Now I don't want to say your wrong or anything but how many marks would I lose for that error? Also will I lose 2 marks for the following question? :frown:

For the sampling distribution, I listed all the possibilites as well as their probabilites but then I didn't put it in a table format. How many marks would I get? 5/6?

Thanks

Not sure how many marks you'll lose without knowing how you got 16/15. You'll lose 1 for the following question as the answer will be wrong.
For the sampling dist I'm not sure. It may be full marks but I'll have to check.
I'll put answers to common questions like this in the first post tomorrow.

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Reply 531

OP

Original post by IAmTheChosenOne

For the sampling distribution, do i need to write it up nicely/ mathematically? I just wrote "probability of being 0 = ........" etc
Will i get full marks?

I think so. I'll double check and answer in he first post.

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Reply 532

Extricated

17

Original post by Gibbo81

Not sure how many marks you'll lose without knowing how you got 16/15. You'll lose 1 for the following question as the answer will be wrong.
For the sampling dist I'm not sure. It may be full marks but I'll have to check.
I'll put answers to common questions like this in the first post tomorrow.

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Gibbo please clear a few things up for me, i'm a bit stressed since I need a good mark in S2!

For the probability of the value being less than 0.5 either side of the mean, my working out was just writing the integrals without actually writing the square brackets thing since I was running out of time but i got 81/128 - do i lose a mark?

how many /5 do you think we're likely to get for poisson instead of binomial on the last q?

Reply 533

Phenylethylamine_

Original post by Gibbo81

I think so. I'll double check and answer in he first post.

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Hey sorry - just one q, for the sampling distribution one instead of doing range, instead I worked out probabilities of the possible combinations. Listed all the combinations and calculated their probabilities and they all added up to one.
Would I at least get 2/6 for it? :frown:

Also - for the probability of mean at least half a minute differing - instead of integrating with the limits 2.5 and 1.5, I did F(2.5) - F(1.5), I quickly found the cdf of the pdf and did that, I got the correct probability as you would when integrating with the limits 2.5 and 1.5 but didn't subtract it from 1. Would I lose only 1 accuracy mark for this? because I didn't get the final answer? as in didn't subtract from 1?

(edited 11 years ago)

Reply 534

Chippyy

Original post by Gemxx

Hello! For the sampling distribution 6 MARKS one, I completely went blank!!
I wrote the mean of number of 1 is: (0.65)^3 + ((0.65)^2 x (0.35) x 3) = 0.71825
The mean of 2 is: 1 - 0.71825= 0.28175
I know I wrote nothing about range or doesn't even remotely look like the markscheme therefore does that mean I'll get 0/6 marks :frown:

... I think I'll just go off and cry!

Well, seeing questions like this before in past papers, previous mark schemes have given 3 marks simply for stating all possible combinations eg (1,1,1) (1,2,1) etc.. So did you write all your combinations down?? If so then you may be given 3 marks.

Reply 535

rfuzzy

Can someone explain that in the grade boundaries table they say the maximum marks for grade boundary have been stated.Does it mean if it says A* at 69 ans A at 64 that 69=100 UMS and 64=90 UMS?

Reply 536

aqua05

does anyone have the unofficial S2 marking scheme for may 2012 ?

Reply 537

knowledgecorruptz