there are 2 sets of data:
X = {0,0,0,4,4,4,6,6,8}
Y = {50,38,56,34,32,42,28,34,29}
There is a negative correlation between X and Y.
Can anyone please explain me. how is the above statement true?
My understanding is as follows:
positive correlation  directly proportional
negative correlation  inversely proportional
Please help me with above question.
Thanks in advance,
Kunal
negative correlation  how?
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 hemant_rajput
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Hi kunal,kunalkulkarni wrote:there are 2 sets of data:
X = {0,0,0,4,4,4,6,6,8}
Y = {50,38,56,34,32,42,28,34,29}
There is a negative correlation between X and Y.
Can anyone please explain me. how is the above statement true?
My understanding is as follows:
positive correlation  directly proportional
negative correlation  inversely proportional
Please help me with above question.
Thanks in advance,
Kunal
Your understanding of negative correlation is perfect. Here, we have two sets, X and Y. These two sets are in negative correlation because, with every increase in the value of element in X, value of element in Y is decreasing.
0  50************************
***********0  38 ************
************************0  56
4  34************************
***********4  32*************
************************4  42
6  28************************
***********6  34*************
************************8  29
I hope this pictorial representation will make it easy for you to comprehend.
Last edited by hemant_rajput on Sun Feb 10, 2013 8:33 pm, edited 1 time in total.
I'm no expert, just trying to work on my skills. If I've made any mistakes please bear with me.

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Hey Hemant,
Thank you for the reply.
So the main catch is to find the transitioning numbers as X changes from 0 to 6. Just to ensure I understood it correctly, if below was the series for X and Y
0  50
0  38
4  42
4  36
6  32
6  40
then it would be impossible to find negative or positive correlation. right?
Thanks,
Kunal
Thank you for the reply.
So the main catch is to find the transitioning numbers as X changes from 0 to 6. Just to ensure I understood it correctly, if below was the series for X and Y
0  50
0  38
4  42
4  36
6  32
6  40
then it would be impossible to find negative or positive correlation. right?
Thanks,
Kunal
 hemant_rajput
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Hi Kunal,
I did some modification in pictorial representation in my previous post. I guess BTG post skips white space in forum. Hope this make it clear.
I did some modification in pictorial representation in my previous post. I guess BTG post skips white space in forum. Hope this make it clear.
I'm no expert, just trying to work on my skills. If I've made any mistakes please bear with me.
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 Tommy Wallach
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Hey Kunal,
You are correct. In that set, there wouldn't be a correlation you could call either positive or negative.
t
P.S. Indeed, BtG does not like white spaces in posts. It's a bit like trying to leave silence on your iPhone voice mail. Ever tried it? No dice.
You are correct. In that set, there wouldn't be a correlation you could call either positive or negative.
t
P.S. Indeed, BtG does not like white spaces in posts. It's a bit like trying to leave silence on your iPhone voice mail. Ever tried it? No dice.
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As per my understanding, correlation is a statistical term with a proper formula. Its value varies from 1 to +1 for any set of data, with value of +1 representing perfect linear positive correlation (data set will draw a straight line in cartesian plane), similarly 1 represents a straight line with negative slope.
Basically, for any given set of data, even random, correlation will be either positive or negative, close to zero for highly uncorrelated/random data.
In the above question, it is clear that when X increases, Y decreases, other than for some exceptions, which can be ignored.
This is my understanding, open for other explanations.
Basically, for any given set of data, even random, correlation will be either positive or negative, close to zero for highly uncorrelated/random data.
In the above question, it is clear that when X increases, Y decreases, other than for some exceptions, which can be ignored.
This is my understanding, open for other explanations.
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 Tommy Wallach
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Hey Mk,
While all that you said may be true, advanced statistics aren't really tested on the GMAT. So you don't need to know much other than a pure positive or a pure negative correlation (i.e. When X goes up, Y goes up; or when X goes down, Y goes up).
t
While all that you said may be true, advanced statistics aren't really tested on the GMAT. So you don't need to know much other than a pure positive or a pure negative correlation (i.e. When X goes up, Y goes up; or when X goes down, Y goes up).
t
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Hey Kunal,
Could you please elaborate on this.
I'm not quite sure that I got this
Cheers,
Taz
Could you please elaborate on this.
I'm not quite sure that I got this
Cheers,
Taz
kunalkulkarni wrote:Hey Hemant,
Thank you for the reply.
So the main catch is to find the transitioning numbers as X changes from 0 to 6. Just to ensure I understood it correctly, if below was the series for X and Y
0  50
0  38
4  42
4  36
6  32
6  40
then it would be impossible to find negative or positive correlation. right?
Thanks,
Kunal
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