s1 - PROBABILITY
Maths and statistics discussion, revision, exam and homework help.
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Re: s1 - PROBABILITYMaybe try posting the question? More people can try to help that way- we don't all have that book.(Original post by otrivine)
this question can someone help me please on edexcel S1 book Mixed exercise 5G question 3)d) not getting it? -
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Re: s1 - PROBABILITYone queries so sxx/syy/ product correlation coefficient /sxy(Original post by TheWorldEndsWithMe)
Maybe try posting the question? More people can try to help that way- we don't all have that book.
what do they get affected by ?
what does mean and S.d get affected by? -
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Re: s1 - PROBABILITYPMCC 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.(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?
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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Re: s1 - PROBABILITYi am sure the mean would increase and the S.D would decrease?(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 dont get the PMCC so does it not get affected at all? -
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Re: s1 - PROBABILITYmean would also increase by 5.(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?
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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Re: s1 - PROBABILITYyes i got it know so SD stays the same right but mean increases and how about sxx/syy/sxy?(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:
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Re: s1 - PROBABILITYi am doing edexcel thankfully we do not need to learn that(Original post by Pride)
do you want me to try and explain spearman's rank as well or are you alright? -
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Re: s1 - PROBABILITYaha ok.(Original post by otrivine)
i am doing edexcel thankfully we do not need to learn that -
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Re: s1 - PROBABILITYhow does sxx/syy/sxy get affected?(Original post by Pride)
aha ok. -
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Re: s1 - PROBABILITYyes 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.(Original post by otrivine)
yes i got it know so SD stays the same right but mean increases and how about sxx/syy/sxy?
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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Re: s1 - PROBABILITYyep i know how to calculate them and to find PMCC easy(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... -
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Re: s1 - PROBABILITYif 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.(Original post by otrivine)
how does sxx/syy/sxy get affected? -
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Re: s1 - PROBABILITYgot it thanks(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. -
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Re: s1 - PROBABILITYSxx will change. I don't know why though XD(Original post by otrivine)
got it thanks
I just did a question and got it wrong thinking it wouldn,t BUT it does! -
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Re: s1 - PROBABILITYwhen does it change ? but does syy/sxy apply the same rule or not?(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! -
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Re: s1 - PROBABILITYNo- it doesn't have the same rule(Original post by otrivine)
when does it change ? but does syy/sxy apply the same rule or not? -
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Re: s1 - PROBABILITYso what will affect sxx/sxy/sxx is it adding substracting '?(Original post by TheHaylio)
No- it doesn't have the same rule
