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# Edexcel S3 - Wednesday 25th May AM 2016 watch

1. (Original post by economicss)
Please could someone explain exercise I question 14A https://771a1ec81340d97ae9ed29694f73...XZCVmc/CH3.pdf Thanks
That is how I would have done it. See my last post where I tried to explain it

(Original post by tazza ma razza)
if we were to use the pmcc instead of sr - would we literally rank them as say 1,2,3,4,5,5.5,5.57,8 for example and then literally just use pmcc by looking at sample level in the table or would we have to calculate say sxy,sxx,syy and then do it like that?
Yeah I think so

2. Attachment 534157534159
Can someone explain this, I don't get their answer. Don't we lose a degree of freedom because we calculated p from the sample? So why didn't they mention that in the answer? Literally all they did was state the obvious, especially considering we had to deal with this in the previous part where we carried a full hypothesis test (with p given to us).
Attached Images

3. (Original post by gagafacea1)

Attachment 534157534159
Can someone explain this, I don't get their answer. Don't we lose a degree of freedom because we calculated p from the sample? So why didn't they mention that in the answer? Literally all they did was state the obvious, especially considering we had to deal with this in the previous part where we carried a full hypothesis test (with p given to us).
Got mugged of by this first time as well. After combining values to make them >5 you have 4 columns and because you have calculated p from the sample v=(4-2). In part c you only do v=(4-1) as p was assumed and not calculated from the sample. Its to do with linear equations connecting values and shiz
4. (Original post by econam)
Got mugged of by this first time as well. After combining values to make them >5 you have 4 columns and because you have calculated p from the sample v=(4-2). In part c you only do v=(4-1) as p was assumed and not calculated from the sample. Its to do with linear equations connecting values and shiz
yeah no I got that, but the reason this part is different from the previous is the fact that p was calculated from the sample, so why would they ignore that in the mark scheme??? God I hate these stupid questions, they're landmines.
5. (Original post by gagafacea1)
yeah no I got that, but the reason this part is different from the previous is the fact that p was calculated from the sample, so why would they ignore that in the mark scheme??? God I hate these stupid questions, they're landmines.
Sorry never saw that you attached the MS. Yeah that is strange, its the main point!
6. (Original post by econam)

Yeah I think so
as in which one lol
7. When do the papers become current syllabus?

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8. (Original post by econam)

That is how I would have done it. See my last post where I tried to explain it

Yeah I think so
Thank you How come we don't divide by the square root of n in this one? Thanks
9. (Original post by gagafacea1)

Attachment 534157534159
Can someone explain this, I don't get their answer. Don't we lose a degree of freedom because we calculated p from the sample? So why didn't they mention that in the answer? Literally all they did was state the obvious, especially considering we had to deal with this in the previous part where we carried a full hypothesis test (with p given to us).
Which paper is this please? Thanks
10. (Original post by economicss)
Which paper is this please? Thanks
revised 2014
11. (Original post by gagafacea1)
revised 2014
Thank you, I don;t suppose you have a link for it please so I can give it a go, can't seem to find it online
12. (Original post by economicss)
Thank you, I don;t suppose you have a link for it please so I can give it a go, can't seem to find it online
I think its this one you're talking about...
https://869d950bf149eefd5cd2652b4001...%20Edexcel.pdf

Oh and the MS:
https://869d950bf149eefd5cd2652b4001...%20Edexcel.pdf
13. (Original post by tazza ma razza)
as in which one lol
My bad, pretty sure you have to do the sxx syy stuff.

(Original post by economicss)
Thank you How come we don't divide by the square root of n in this one? Thanks
'Just to add a little to what coolguy said. Part a is asking for range of heights for all the individual orchids and part b asking for the range of the mean. The more samples you take to find the mean you would expect to get closer to its true value. This means when finding a confidence interval for the means you divide standard dev by rootn and as a result get a smaller range.

Because in part a you are looking at the range of values for just the orchids you just multiply by standard dev. Getting a larger range, as you would expect when looking at the range of individual orchids.'

From my previous post - hope that clears it up. Same applies just with sugar instead.
14. (Original post by physicsmaths)
When do the papers become current syllabus?

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Bump

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15. (Original post by physicsmaths)
Bump

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I think around 2009-2010. The papers become noticeably more difficult too!
16. Anyone have any combinations of random variables questions? Tough ones?

Couldn't find a booklet on TeeEm's site

Just taken a look at the one in last year's paper and I'm not prepared
17. (Original post by econam)
June 2012. You dont have to do it, just explain what you would do.
that seems really dodgy, why can't you calculate SPCC with tied ranks?

also, PMCC can only be calculated if the variables are normally distributed and the question doesnt say they are?
18. (Original post by Euclidean)
Anyone have any combinations of random variables questions? Tough ones?

Couldn't find a booklet on TeeEm's site

Just taken a look at the one in last year's paper and I'm not prepared
The key thing is understanding the difference between adding multiple distributions (it's usually men and women's weight or stuff like that) and multiplying one distribution.

Eg if M~N(a,b) and W~N(c,d) then the difference between a man and a woman's weight would be ~N(a-c, b+d) but if you were asked for the probability of a man's height being 1.5 times more than a woman's, you'd be looking for something like (D :=M-1.5W)~N(a-1.5c,b+2.25d) and you'd find P(D>0) and.. that's about it.
19. Guys, I am about to start teaching the module. I know it's late but yeah, how long did it take you guys to complete? Thanks.

EDIT: Also, are there any topics you would recommend going over from S1 or S2 as it has been a year since I've looked at them.
Guys, I am about to start teaching the module. I know it's late but yeah, how long did it take you guys to complete? Thanks.

EDIT: Also, are there any topics you would recommend going over from S1 or S2 as it has been a year since I've looked at them.
Normal distribution if you're not very confident with it

Otherwise it took me around 5 hours to study from scratch, the bulk of that being chapter 2 tbh

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