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# Statistics S1B 17/05/2013 Thread Watch

1. (Original post by davidbaroi)
is this edexcel?
No, AQA
2. This is the rest of my answers for 6a

Not entirely sure about the why the CLT not required is right for mine

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3. I have no idea what I did.....
4. (Original post by Son234)
This is the rest of my answers for 6a

Not entirely sure about the why the CLT not required is right for mine

This was posted from The Student Room's iPhone/iPad App
I think for the CLT, all we had to say was that it was a normal distribution.
5. Did anyone put the unbiased estimate of standard deviation, 17.5 i think, for for the first part of question 1????
6. I got 27 for the last part of question 3.
7. (Original post by Gotzz)
I think for the CLT, all we had to say was that it was a normal distribution.
It says on the question modelled by a normal random variable

That's why I didn't put it was normally distributed

And CLT is only valid for n>30 big large sample size

So to me it made sense to use 25 ==> n<30

It was 1 Mark too so I'm not that bothered

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8. (Original post by the_googly)
I got 27 for the last part of question 3.
So did I!
9. (Original post by Son234)
It says on the question modelled by a normal random variable

That's why I didn't put it was normally distributed

And CLT is only valid for n>30 big large sample size

So to me it made sense to use 25 ==> n<30

It was 1 Mark too so I'm not that bothered

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Okay I'm not too sure then. It was just that I remember doing some a similar question in a past paper and it said that and didn't allow the sample size point.
Maybe you're right.
10. Was it 27 or 14 for the last part of Question 3?
11. (Original post by 002)
Was it 27 or 14 for the last part of Question 3?
27
12. Anybody want to the whole paper and upload it like somebody did with C1 and C2? :-)
13. (Original post by Gotzz)
27
Why?
14. (Original post by Son234)
It says on the question modelled by a normal random variable

That's why I didn't put it was normally distributed

And CLT is only valid for n>30 big large sample size

So to me it made sense to use 25 ==> n<30

It was 1 Mark too so I'm not that bothered

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Normal random variables are distributed normally. You just had to say that it is known that it is normally distributed so CLT is unecessary.

I'm not sure whether you'll get a mark for saying 25 is smaller than 30, so it's not valid. Technically, 25 is an acceptable sample size.
15. (Original post by 002)
Why?
0.85 - 0.175 = 0.675
0.675 x 40 = 27
16. (Original post by MrJiggly)
Normal random variables are distributed normally. You just had to say that it is known that it is normally distributed so CLT is unecessary.

I'm not sure whether you'll get a mark for saying 25 is smaller than 30, so it's not valid. Technically, 25 is an acceptable sample size.
Would you have to specifically say "it is known"? Or do you think saying it is normally distributed is enough?
17. (Original post by Gotzz)
Would you have to specifically say "it is known"? Or do you think saying it is normally distributed is enough?
Probably just have to mention the words : "Normally distributed"...

at least I hope so...
18. Here's my exact answers to question 3

I can categorically say the answer to part b in question 3 is 27 not 14

I lost 2 marks but i have shown the answer anyway

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19. (Original post by MrJiggly)
Probably just have to mention the words : "Normally distributed"...

at least I hope so...
Me too!
20. How can the answer to the last part of the question possibly be 27?! If it was 27, the probability used would be 0.675. With this probability, is would have been impossible to answer the binomial distribution question which went before it, as 0.675 is not on the binomial tables, whereas 0.35 is (0.35 x 40= 14). Sorry to break it to you guys, but 14 is clearly the correct answer to the last part of question 3.

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