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s1 - PROBABILITY

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    this question can someone help me please on edexcel S1 book Mixed exercise 5G question 3)d) not getting it?
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    (Original post by otrivine)
    this question can someone help me please on edexcel S1 book Mixed exercise 5G question 3)d) not getting it?
    Maybe try posting the question? More people can try to help that way- we don't all have that book.
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    As shown by the diagram I have drawn using my amazing artistic skills, 4 people are left-handed and female (including the centre area).

    How many of those 4 also wear glasses? (big hint, look in the centre again. :P )
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    (Original post by TheWorldEndsWithMe)
    Maybe try posting the question? More people can try to help that way- we don't all have that book.
    one queries so sxx/syy/ product correlation coefficient /sxy
    what do they get affected by ?
    what does mean and S.d get affected by?
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    (Original post by otrivine)
    one queries so sxx/syy/ product correlation coefficient /sxy
    what do they get affected by ?
    what does mean and S.d get affected by?
    PMCC is a measure of how close to perfect correlation the data is. If the data becomes more like the trend, or veers away from the trend, PMCC'll change. r = +1 is perfect correlation.

    mean and std dev. OK there's a question that always comes up, to make sure ppl understand mean and std dev.

    Imagine there's a set of data. Now if I decided that every value in that data should increase by 5, how would the mean and std dev be affected?
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    (Original post by Pride)
    PMCC is a measure of how close to perfect correlation the data is. If the data becomes more like the trend, or veers away from the trend, PMCC'll change. r = +1 is perfect correlation.

    mean and std dev. OK there's a question that always comes up, to make sure ppl understand mean and std dev.

    Imagine there's a set of data. Now if I decided that every value in that data should increase by 5, how would the mean and std dev be affected?
    i am sure the mean would increase and the S.D would decrease?
    i dont get the PMCC so does it not get affected at all?
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    (Original post by otrivine)
    i am sure the mean would increase and the S.D would decrease?
    i dont get the PMCC so does it not get affected at all?
    mean would also increase by 5.
    Std dev WOULD NOT CHANGE AT ALL. This (and variations of what I've just said) always comes up. Remember this. When you change each value by the same amount, the std dev or variance does not change.

    PMCC is how close to perfect correlation a set of data is. You'll have been given equations for working it out, and taught how to get it on a graphical calculator by putting in data.

    this is a really great image that tells you what I mean, product moment correlation coefficient is r:
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    do you want me to try and explain spearman's rank as well or are you alright?
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    (Original post by Pride)
    mean would also increase by 5.
    Std dev WOULD NOT CHANGE AT ALL. This (and variations of what I've just said) always comes up. Remember this. When you change each value by the same amount, the std dev or variance does not change.

    PMCC is how close to perfect correlation a set of data is. You'll have been given equations for working it out, and taught how to get it on a graphical calculator by putting in data.

    this is a really great image that tells you what I mean, product moment correlation coefficient is r:
    yes i got it know so SD stays the same right but mean increases and how about sxx/syy/sxy?
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    (Original post by Pride)
    do you want me to try and explain spearman's rank as well or are you alright?
    i am doing edexcel thankfully we do not need to learn that
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    (Original post by otrivine)
    i am doing edexcel thankfully we do not need to learn that
    aha ok.
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    (Original post by Pride)
    aha ok.
    how does sxx/syy/sxy get affected?
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    (Original post by otrivine)
    yes i got it know so SD stays the same right but mean increases and how about sxx/syy/sxy?
    yes mean increases because the mean is the average of the results, if each one goes up by 5, the mean'll go up by 5.

    Std dev/variance, is how close to the mean the data tends to be, so if all of em increase by the same amount, they haven't actually moved any further from the mean, because the mean increases too... hope that makes sense.

    What do you know about sxx, syy, sxy already? Do you know how to calculate them? You know you use those to calculate r (PMCC)

    in ocr, we don't go too deep into what they actually mean, we just calculate sxx syy...
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    (Original post by Pride)
    yes mean increases because the mean is the average of the results, if each one goes up by 5, the mean'll go up by 5.

    Std dev/variance, is how close to the mean the data tends to be, so if all of em increase by the same amount, they haven't actually moved any further from the mean, because the mean increases too... hope that makes sense.

    What do you know about sxx, syy, sxy already? Do you know how to calculate them? You know you use those to calculate r (PMCC)

    in ocr, we don't go to deep into what they actually mean, we just calculate sxx syy...
    yep i know how to calculate them and to find PMCC easy
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    (Original post by otrivine)
    how does sxx/syy/sxy get affected?
    if all data increases by the same amount, r wouldn't change, I don't really know if sxx etc will change, I just know the correlation will remain the same.
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    (Original post by Pride)
    if all data increases by the same amount, r wouldn't change, I don't really know if sxx etc will change, I just know the correlation will remain the same.
    got it thanks
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    (Original post by otrivine)
    got it thanks
    Sxx will change. I don't know why though XD

    I just did a question and got it wrong thinking it wouldn,t BUT it does!
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    (Original post by TheHaylio)
    Sxx will change. I don't know why though XD

    I just did a question and got it wrong thinking it wouldn,t BUT it does!
    when does it change ? but does syy/sxy apply the same rule or not?
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    (Original post by otrivine)
    when does it change ? but does syy/sxy apply the same rule or not?
    No- it doesn't have the same rule
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    (Original post by TheHaylio)
    No- it doesn't have the same rule
    so what will affect sxx/sxy/sxx is it adding substracting '?

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Updated: May 17, 2012
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