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

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?

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?

Reckon you could get 3 or 4 max for the sampling dist. You'll probably lose 1 for 5d).

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?

Yep I'm afraid you probably will.

Sounds like a plan!


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You may be lucky with 5d and get full marks. The fact that it is only 3 means they may not need to see the actual integral.

I think you'll lose 3/5 on q8a but you might be lucky and only lose 2.

You may be lucky with 5d and get full marks. The fact that it is only 3 means they may not need to see the actual integral.

I think you'll lose 3/5 on q8a but you might be lucky and only lose 2.

In the jan 2012 paper, there was a similar question, asking you to sketch pdf, but in the mark scheme, there were no marks for the bold bits, just marks for the shape, and the axis interceptions. Do you reckon our mark scheme will be the same?

A quick scan of some mark schemes has 'condone missing patios' or 'ignore missing patios' next to a graph... i have no idea what a 'patio' is on a graph i assume its the flat bit, so i think u wont lose the marks.

In the jan 2012 paper, there was a similar question, asking you to sketch pdf, but in the mark scheme, there were no marks for the bold bits, just marks for the shape, and the axis interceptions. Do you reckon our mark scheme will be the same?

A quick scan of some mark schemes has 'condone missing patios' or 'ignore missing patios' next to a graph... i have no idea what a 'patio' is on a graph i assume its the flat bit, so i think u wont lose the marks.

I dissagree in alot of the markscheme's the lines are in bold. However i'm in the same boat so i just hope you are right.

Yes yes but if you read the notes after the question is always says 'condone missing patios'. The june 2010 one highlights them then says 'condone missing patios', the next mark scheme says 'ignore missing patios (y=0 lines). So no you won't.

I hope your right but on a seperate note.. Why have them in bold then

I have no idea, because they are conventionally drawn but not hugely important concerning awarding marks?. Anyway did anything find out how the other 1 mark would be dealt with on question 3 where people used poisson on there Ho instead of bin, i mean its valid but would it get the marks...

I have no idea, because they are conventionally drawn but not hugely important concerning awarding marks?. Anyway did anything find out how the other 1 mark would be dealt with on question 3 where people used poisson on there Ho instead of bin, i mean its valid but would it get the marks...

Was the q about finding the probability of the mean differing by half minute 2 or 3 marks?

it was 3 mate

Reckon you could get 3 or 4 max for the sampling dist. You'll probably lose 1 for 5d).

Q8, marks gone. Assuming ill get atleast two marks for attempting the answer with a poisson distribution i lost a solid 5 marks. I drew a tree diagram, listed the samples, but i drew the distribution table in another away. In stead of 2 outcomes i had 4, each being like - either 2 Number 1's and 1 Number 2, 3 Number 1's, 3 Number 2's, or 2 Number 2's and 1 number 1 and so on. My values were correct...will I get marks on that?
I also seemed to have gotten my probability incorrect region wrong i wrote 0.0216+0.0216....but i should get a mark for that and I gotten the last part for C incorrect of the three cumulative function. So i lost about a solid 7 marks, along with of those in the sampling distribution. I'll say ill get around 63+...hopefully an A.. -_-

Okay, thanks! This makes me feel much better