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# Statistics S1B 17/05/2013 Thread Watch

1. (Original post by Tha Realest)
I think there is going to be a really nasty probability question

And a completely new question that hasn't been in any of the previous papers :|

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2. (Original post by Son234)
I think there is going to be a really nasty probability question

And a completely new question that hasn't been in any of the previous papers :|

This was posted from The Student Room's iPhone/iPad App
Haha ~ Calm It
3. (Original post by Son234)
I think there is going to be a really nasty probability question

And a completely new question that hasn't been in any of the previous papers :|

This was posted from The Student Room's iPhone/iPad App
'The probability of you getting full marks on this question is 0.01. The probability of you getting full marks on this question given that the rest of the people in this room get full marks is 0.001. Calculate the probability that a comet is going to fall from space and destroy the exam room'.
4. (Original post by Son234)
I think there is going to be a really nasty probability question

And a completely new question that hasn't been in any of the previous papers :|

This was posted from The Student Room's iPhone/iPad App
Oh well done. Now you have jinx'd it!
5. (Original post by RoseBrilliante)
'The probability of you getting full marks on this question is 0.01. The probability of you getting full marks on this question given that the rest of the people in this room get full marks is 0.001. Calculate the probability that a comet is going to fall from space and destroy the exam room'.
Lol that means I'm independent

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6. (Original post by RoseBrilliante)
'The probability of you getting full marks on this question is 0.01. The probability of you getting full marks on this question given that the rest of the people in this room get full marks is 0.001. Calculate the probability that a comet is going to fall from space and destroy the exam room'.
Haha lol
7. A machine, which cuts bread dough for loaves, can be adjusted to cut dough to any specified set weight. For any set weight, m grams, the actual weights of cut dough are known to be approximately normally distributed with a mean of m grams and a fixed standard deviation of s grams.

It is also known that the machine cuts dough to within 10 grams of any set weight.

7A))Estimate, with justification, a value for s. (2 marks) The machine is set to cut dough to a weight of 415 grams.

She then asked him to calculate the mean and the standard deviation of his 15 recorded weights.

Dev subsequently reported to Sunita that, for his sample, the mean was 391 grams and the standard deviation was 95.5 grams.

7B))Advise Sunita on whether or not each of Dev’s values is likely to be correct. Give numerical support for your answers.

Can someone please explain the answers to the 2 above questions from the AQA S1 Jan 13 Thanks.
8. If you are given two variables X and Y, how can you determine if they are independent by using the mean or variance?
9. (Original post by the_googly)
If you are given two variables X and Y, how can you determine if they are independent by using the mean or variance?
You should be given the probability of x and y

And the sample size of x and y

Calculate the mean and variance of both x and y

Using np and npq

Compare and if the variance is not the same for both x and y then it is independent

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10. (Original post by Son234)
You should be given the probability of x and y

And the sample size of x and y

Calculate the mean and variance of both x and y

Using np and npq

Compare and if the variance is not the same for both x and y then it is independent

This was posted from The Student Room's iPhone/iPad App
Thanks a lot. Is it possible to compare the mean instead of the variance?
11. (Original post by the_googly)
Thanks a lot. Is it possible to compare the mean instead of the variance?
Yeah compare both it might be that mean are same variance is different

Or both different

Or mean different and variance same

Use that info to answer the question

But depends on the context of the question

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12. Anyone please quickly explain question 7(a) and 7(b) from the AQA January 2013 S1 paper thanks ...

Cheers
13. Good luck guys, hope we all to well, the exam is in 90mins
14. (Original post by Tha Realest)
Anyone please quickly explain question 7(a) and 7(b) from the AQA January 2013 S1 paper thanks ...

Cheers
It's quite annoying that all these stats experts avoided this question, was hoping to wake up today and see a soluion
15. (Original post by niceguy95)
It's quite annoying that all these stats experts avoided this question, was hoping to wake up today and see a soluion
7a 99.9% of distribution lie within 3st. of the mean so Sigma = 10/3 = 3.333
B
415-10, 415+10

• 405 – 425

Min acceptable weight is 405
391<405 à dough is cut too small (mean of sample is smaller)
If sigma=95.5 then 95.5>3
So both values are likely to be incorrect

C
for question c), you do (sum of y)/n which is 821, so it is within the stated value of 820 g so acceptable.. [(sum of x-xbar)^2]/srqt(n-1), and you will get a s.d of 3.3 which is similar to the previous answer in (a)
16. (Original post by niceguy95)
It's quite annoying that all these stats experts avoided this question, was hoping to wake up today and see a soluion
7a)

All your points lie within the range of mean+- 3Standard deviation

10=3SD

10\3=3.3333 simple

7c) Last calculate mean 8210/10

And variance 110/10=11

standard deviation = 3.31

Both Standard deviation and means similar values likely to be true

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17. 7b I just finished the paper it's exactly mentioned above ^^

415+- 10 = 405

Claim mean 391<405

Standard deviation 95.5>3.33 from part 7a

Neither values are likely to be correct

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18. Q1 on June 13 paper we just sat, the standard deviation stays the same after converting °F to ° C right ?????????
so sd= 15.7 or something like that?
19. So how does everyone think it went?
Q1 on June 13 paper we just sat, the standard deviation stays the same after converting °F to ° C right ?????????
so sd= 15.7 or something like that?
I got a - number so i know im wrong and thinking of it i believe it doesnt change as well.

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