# Maths PMCC values

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#1
Would a PMCC value of -0.8 be greater than a value of 0.6 because -0.8 would suggest that the values are closer together or what would it be 0.6 because its positive?
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10 months ago
#2
(Original post by Helpstudent402)
Would a PMCC value of -0.8 be greater than a value of 0.6 because -0.8 would suggest that the values are closer together or what would it be 0.6 because its positive?
It depends what you mean by "greater". If you mean "which has the biggest linear correlation", then yes, it is the -0.8, because it is closer to -1 than 0.6 is to 1. It is of course telling you that the correlation is negative.
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#3
(Original post by Pangol)
It depends what you mean by "greater". If you mean "which has the biggest linear correlation", then yes, it is the -0.8, because it is closer to -1 than 0.6 is to 1. It is of course telling you that the correlation is negative.
So if I was just asked for greater, it wouldn't make any sense?
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10 months ago
#4
(Original post by Helpstudent402)
So if I was just asked for greater, it wouldn't make any sense?
It probably means which shows the largest correlation, but it needs to be clearer to be sure. What is the exact wording of the question?
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#5
(Original post by Pangol)
It probably means which shows the largest correlation, but it needs to be clearer to be sure. What is the exact wording of the question?
I can't remember exactly but it showed 4 graphs and 2 of them had a positive correlation but neither were greater than about 0.6 (estimate), there was one graph that had all points in a straight line so PMCC would = 0 and another graph that had a strong negative correlation around -0.8. The Q asked which graph has the greatest PMCC value
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10 months ago
#6
(Original post by Helpstudent402)
I can't remember exactly but it showed 4 graphs and 2 of them had a positive correlation but neither were greater than about 0.6 (estimate), there was one graph that had all points in a straight line so PMCC would = 0 and another graph that had a strong negative correlation around -0.8. The Q asked which graph has the greatest PMCC value
It probably does mean the strongest linear correlation, positive or negative.

Are you sure that the graph with all the points on a straight line would have a PMCC of zero? Why?
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#7
(Original post by Pangol)
It probably does mean the strongest linear correlation, positive or negative.

Are you sure that the graph with all the points on a straight line would have a PMCC of zero? Why?
I mean a straight line where y=x, it would have a PMCC of 0 because y would not depend on x.
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10 months ago
#8
(Original post by Helpstudent402)
I mean a straight line where y=x, it would have a PMCC of 0 because y would not depend on x.
Do you mean a straight line where y = constant?
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#9
(Original post by Pangol)
Do you mean a straight line where y = constant?
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10 months ago
#10
a PMCC of 1 is perfect positive correlation
0 is no correlation
-1 is perfect negative correlation

and values in between are... in between

so when the PMCC is -0.8 there is more correlation between x and y than when PMCC = 0.6
ie the values in the -0.8 set lie closer to their line of best fit, the 0.6 set values are a little more scattered around their line of best fit
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