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    How did everyone end up doing S2?
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    I've barely started s2 yet. Because it's only for the AS, I don't need it si I've neglected it. Only hoping for a C tbh
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    (Original post by ChoccyPhilly)
    I've barely started s2 yet. Because it's only for the AS, I don't need it si I've neglected it. Only hoping for a C tbh
    You can learn S2 in quite a short time, it's only about 7 chapters and the ones on hypothesis tests and sampling are pretty much the same.
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    (Original post by lllllllllll)
    You can learn S2 in quite a short time, it's only about 7 chapters and the ones on hypothesis tests and sampling are pretty much the same.
    Yeah I'm gonna spend a day or two during half term JUST doing s2 work from scratch. Should be... Interesting
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    Best revision places online? I find S2 so freaking hard; I can't do Hypothesis testing, which is basically half of the paper.
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    (Original post by Sam596)
    Best revision places online? I find S2 so freaking hard; I can't do Hypothesis testing, which is basically half of the paper.
    I was looking at exam solutions, I can't believe Edexel don't have this!! I just learnt it by bashing my way through the book. Wasn't the most time-effective way to do it but it eventually worked

    Edit: Oh wait.. They do have it

    http://www.examsolutions.net/maths-r.../S2/module.php
    but it seems they only do discrete random variables. Still worth looking at though
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    (Original post by lllllllllll)
    I was looking at exam solutions, I can't believe Edexel don't have this!! I just learnt it by bashing my way through the book. Wasn't the most time-effective way to do it but it eventually worked

    Edit: Oh wait.. They do have it

    http://www.examsolutions.net/maths-r.../S2/module.php
    but it seems they only do discrete random variables. Still worth looking at though
    http://www.furthermaths.org.uk/ocr-revision is what i've found and using now.
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    (Original post by Sam596)
    http://www.furthermaths.org.uk/ocr-revision is what i've found and using now.
    That guy is also very good Haven't watched any of his videos in a while though
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    Hey guys, can anyone help me with deciding when to divide the varience of something by the sample size? Simple I know but I can't get my head around it
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    (Original post by James_Tait)
    Hey guys, can anyone help me with deciding when to divide the varience of something by the sample size? Simple I know but I can't get my head around it
    You divide by the sample size when you're asked about probabilities regarding a sample. No matter how the population is distributed, providing n is large, the central limit theorem says the sample mean can be approximated by X-N(mean, variance/sample size).
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    For continuity corrections, how do we know when we should use  \dfrac{1}{2n} as the continuity correction.…and which scenario do we use  Var(n(X)) = \dfrac{s^2}{n} instead of  Var(n(X)) = \dfrac{\sigma^2}{n} ?
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    You use 1/2n when the initial distribution is discrete. So if the initial distribution was X-B(40,0.2) you can approx that to X-N(8, 6.4) then to get the distribution for the sample of size n you get X(bar)-N(8,6.4/n) and say you were looking for P(X(bar) <=10), because the distribution at the start was binomial you use a 1/2n continuity correction instead of 0.5.
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    (Original post by Tomh97)
    You use 1/2n when the initial distribution is discrete. So if the initial distribution was X-B(40,0.2) you can approx that to X-N(8, 6.4) then to get the distribution for the sample of size n you get X(bar)-N(8,6.4/n) and say you were looking for P(X(bar) <=10), because the distribution at the start was binomial you use a 1/2n continuity correction instead of 0.5.
    Oh I see, so it's CLT for discrete variables?


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    (Original post by lllllllllll)
    Oh I see, so it's CLT for discrete variables?


    Posted from TSR Mobile
    The CLT says that if a sample is sufficiently large the distribution of the sample mean is approximated by X-N(mean, variance/n), no matter what the underlying distribution is.
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    (Original post by Tomh97)
    The CLT says that if a sample is sufficiently large the distribution of the sample mean is approximated by X-N(mean, variance/n), no matter what the underlying distribution is.
    Think I understand it slightly better now. June 2013 Q6 is a very good example to practice. Thanks
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    Hiya I'll be sitting this tomorrow, feeling okay about it so fingers crossed!

    Would someone possibly be able to help me with this question though? Question 4 on Jan 2012. I have the right method but I don't understand why or how they've standardised it?

    Thank you
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    (Original post by Molly_xox)
    Hiya I'll be sitting this tomorrow, feeling okay about it so fingers crossed!

    Would someone possibly be able to help me with this question though? Question 4 on Jan 2012. I have the right method but I don't understand why or how they've standardised it?

    Thank you
    Really hope this goes well after the train wreck that was M2.

    It's standardised because it's the sample mean of H so you divide the variance by 50. Hope that helps!
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    (Original post by Molly_xox)
    Hiya I'll be sitting this tomorrow, feeling okay about it so fingers crossed!

    Would someone possibly be able to help me with this question though? Question 4 on Jan 2012. I have the right method but I don't understand why or how they've standardised it?

    Thank you
    Because the initial R.V was said to be discrete you use a continuity correction of 1/2n instead of the usual 0.5. Because they want <2.6 you do 2.6-1/(2*50), because there were 50 observations.
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    (Original post by tbhlouise)
    Really hope this goes well after the train wreck that was M2.

    It's standardised because it's the sample mean of H so you divide the variance by 50. Hope that helps!
    Here's hoping! Fingers crossed for your M2 result too.

    Okay...this concept is completely new to me! I know that the variance has to be divided by 50, so it becomes

    H(sample) ~ N(2.5, 1.25/50)

    But I'm not sure why that applies to the 2.6? And why does it get standardised to 2.59 as opposed to, say, 2.55?

    I'm sorry if I'm being really thick here thanks for your help so far!

    Edit:
    (Original post by Tomh97)
    Because the initial R.V was said to be discrete you use a continuity correction of 1/2n instead of the usual 0.5. Because they want <2.6 you do 2.6-1/(2*50), because there were 50 observations.
    I didn't see this before I posted, thank you! So every time the variable is discrete you just use that? Thank you!
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    (Original post by Tomh97)
    Because the initial R.V was said to be discrete you use a continuity correction of 1/2n instead of the usual 0.5. Because they want <2.6 you do 2.6-1/(2*50), because there were 50 observations.
    Oh right! Forgot what 'standardise' meant whilst I was writing . I really can't afford to be this stupid tmr
 
 
 
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