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# Edexcel S3 - Wednesday 25th May AM 2016 watch

1. (Original post by Zacken)
Generally, if it's not too much trouble, I would do it both ways to make sure my answer is correct. (they amount to the same thing, although a bit of care has to be taken w.r.t decimal places rounding) If it was an annoying calculation where the class was >= 6 and I'd need to look up cumulative crap in the tables, then I'd just add up the previous ones and do total - (sum of previous).
Actually, that makes sense. Cuz that question I did before (where the mark scheme did the adding up method), I remember it being a class like >=6. So definitely the mark scheme agrees with you. Thanks!
2. (Original post by Geraer1)
Okay thanks! And in this paper, actually one part of q6 involves pooling two columns together as one of the expected frequencies is below 5 for a contingency table. So it did appear in a paper!
(Original post by Zacken)
Yes, June 15. You had to explain why, but you didn't actually have to combine it yourself which was what I was talking about.
Yeah, someone brought that up yesterday.
3. (Original post by Zacken)
Yeah, someone brought that up yesterday.
Ah okay!
4. (Original post by Music With Rocks)
Is there ever a time in S3 when you would use the σ2rather than S2 formula?
What is the σ2 formula?
5. Quick question:

You must combine classes for continuous uniform if E is less than 5, right?

(I know that the same goes for all other chi-sqaured tests)
6. (Original post by zaybun)
When they ask you to calculate the biased variance as opposed to the unbiased one I'm guessing.
Anything can be a biased estimator of variance.

(Original post by Rkai01)
Could we actually be asked to calculate c in a pdf and those type questions?

I can't remember much of those s2 things
Yes, they certainly could but most likely wouldn't given the repetitive nature/style of S3 past papers.
7. (Original post by physicsmaths)
+-0.6mm so the modulus of the difference.
This is very known and comes up tonnes go over it in the book.
when was that paper?
8. (Original post by zaybun)
Quick question:

You must combine classes for continuous uniform if E is less than 5, right?

(I know that the same goes for all other chi-sqaured tests)
Yes.
9. (Original post by Zacken)
Yes.
Thank you! Teacher did an example months back and I just had a look through my notes and I guess she forgot to combine the classes
10. (Original post by tazza ma razza)
when was that paper?
2011 or 2010 not sure.

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11. (Original post by physicsmaths)
2011 or 2010 not sure.

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(Y)
12. (Original post by tazza ma razza)
when was that paper?
June 2010, iirc.

(Original post by zaybun)
Thank you! Teacher did an example months back and I just had a look through my notes and I guess she forgot to combine the classes
Yep, must be.
13. Has anyone got a link to last years paper?
14. (Original post by Messier31)
Has anyone got a link to last years paper?
Check the Edexcel website
15. (Original post by Messier31)
Has anyone got a link to last years paper?
Im about to do that one aswell.
Report back in abit.

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16. (Original post by tazza ma razza)
(Y)
?

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17. (Original post by Euclidean)
Check the Edexcel website
Oh

Thanks

(Original post by physicsmaths)
Im about to do that one aswell.
Report back in abit.

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I'll be expecting you in about half an hour
18. *thumbs up*
19. (Y) is a thumbs up emoji, probably not what you think
20. (Original post by Euclidean)
(Y) is a thumbs up emoji, probably not what you think
My thoughts exactly when I first came across it.

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