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Official Edexcel S3 thread Wednesday 20 May 2015 Morning [6691] watch

1. Hi there guys, has anyone got a markscheme definition to confidence intervals? E.g. 95% or whatever. Thanks!
2. (Original post by JaiGuruji)
Hi there guys, has anyone got a markscheme definition to confidence intervals? E.g. 95% or whatever. Thanks!
There's no mark scheme definition because you are never asked to define it (out of context at least) but I can give you my best definition/explanation if you want.
3. (Original post by JaiGuruji)
Hi there guys, has anyone got a markscheme definition to confidence intervals? E.g. 95% or whatever. Thanks!
(Original post by STATER)
There's no mark scheme definition because you are never asked to define it (out of context at least) but I can give you my best definition/explanation if you want.
There is actually a mark scheme definition, it's this: "A 95% confidence interval is an interval within which we are 95% confident mew lies" literally that easy. Can't remember what paper exactly but it definitely came up in a past paper (perhaps before 2005).
4. I found an extra IAL paper, albeit sample assessment material. Still probably better practice than standard edexcel papers.

http://qualifications.pearson.com/co...all%20file.pdf

It's on page 379 of the PDF.
5. (Original post by STATER)
I found an extra IAL paper, albeit sample assessment material. Still probably better practice than standard edexcel papers.

http://qualifications.pearson.com/co...all%20file.pdf

It's on page 379 of the PDF.
You hero.

Holy smokes 46 marks on hypothesis testing lol!
6. Suggestions for S3 specific best practices regarding accuracy of answers?

It seems the standard 3 sig. figures rule applies most of the time but sometimes it appears not to. I would've assumed this would be from table values but sometimes they have awrt 3sf values.
7. (Original post by Iridann)
Suggestions for S3 specific best practices regarding accuracy of answers?

It seems the standard 3 sig. figures rule applies most of the time but sometimes it appears not to. I would've assumed this would be from table values but sometimes they have awrt 3sf values.
In every paper I have done awrt to 3 (sometimes 4) dp has applied. I've done the recent papers (2010 -2014) so answers to 4dp are safe. They don't penalise you for being too accurate (with the exception of fraction form), so you can leave as many dp as you wish.
8. (Original post by STATER)
In every paper I have done awrt to 3 (sometimes 4) dp has applied. I've done the recent papers (2010 -2014) so answers to 4dp are safe. They don't penalise you for being too accurate (with the exception of fraction form), so you can leave as many dp as you wish.
Ah I did not know that one! Thanks, I always assumed you got penalised for giving too many figures as a final answer.

Do they accept it when you add (...) after 3/4 decimal places as well do you know?
9. (Original post by Iridann)
Ah I did not know that one! Thanks, I always assumed you got penalised for giving too many figures as a final answer.

Do they accept it when you add (...) after 3/4 decimal places as well do you know?
They accept (...) for working, but as far as I know, not for the final answer.
10. (Original post by Damien_Dalgaard)
I think by doing the ial's/ r papers it makes the normal papers easier at least in my opionion.

I remember your username, you must be have been here for a while.

You going Cambridge or something :d

Thank you very much, I will practice this later.

I salute you sir.
Where can I access the IAL papers?
Where can I access the IAL papers?
http://www.physicsandmathstutor.com/...dexcel-papers/
12. Thank you so much for sharing this! I needed new material to practise
I'm so nervous for the exam
13. (Original post by xKay)
There is actually a mark scheme definition, it's this: "A 95% confidence interval is an interval within which we are 95% confident mew lies" literally that easy. Can't remember what paper exactly but it definitely came up in a past paper (perhaps before 2005).
That isn't what a 95% confidence interval means?

It means: If we repeat the experiment lots of times, 95% of the time the actual value of will lie in the confidence interval.
14. (Original post by rayquaza17)
That isn't what a 95% confidence interval means?

It means: If we repeat the experiment lots of times, 95% of the time the actual value of will lie in the confidence interval.
Look at exercise 3i in the s3 book question 10b (page 59)
15. (Original post by rayquaza17)
That isn't what a 95% confidence interval means?

It means: If we repeat the experiment lots of times, 95% of the time the actual value of will lie in the confidence interval.
Forgive me if I am wrong but aren't these saying the same thing?
16. (Original post by Gome44)
Forgive me if I am wrong but aren't these saying the same thing?
You need to include the thing about repeated samples though.

(Original post by xKay)
Look at exercise 3i in the s3 book question 10b (page 59)
I don't have the book. I'm not sitting this exam.

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17. (Original post by xKay)
Look at exercise 3i in the s3 book question 10b (page 59)
you m

(Original post by xKay)
There is actually a mark scheme definition, it's this: "A 95% confidence interval is an interval within which we are 95% confident mew lies" literally that easy. Can't remember what paper exactly but it definitely came up in a past paper (perhaps before 2005).
is it possible for you to find that particular paper, it will be extremely helpful, thanks!
18. (Original post by rayquaza17)
That isn't what a 95% confidence interval means?

It means: If we repeat the experiment lots of times, 95% of the time the actual value of will lie in the confidence interval.
If this were the definition of a confidence interval, then why would the confidence interval use the sample mean of only one sample? Repeating an experiment lots of times kinda goes against this.
19. Does anyone have a list of all the definitions we need to know?
20. (Original post by rayquaza17)
You need to include the thing about repeated samples though.
I think you're trying to say that the sample has to be large enough, since a confidence interval is calculated for individual samples. The sample size must be large enough so that it may be assumed by the central limit theorem that the sample mean is normally distributed. And the x% confidence interval tells you the x% probability that the population mean lies within that interval.

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