# Please can someone help with Correlation coefficient

• Apr 3rd 2009, 10:14 AM
rose
Please can someone help with Correlation coefficient
Hi

I am really struggling with finding the correlation coefficient for this set of data:

1991 947
1992 1098
1993 1108
1994 1107
1995 1615
1996 2282
1997 2766
1998 2505
1999 2501
2000 2637

I think I know the formula I just dont ever seem to be able to get an answer.

Thank you
• Apr 3rd 2009, 04:07 PM
matheagle
The correlation coefficient is the ratio of the covariance over the standard deviations.
In this case it would be smart to subtract off a number like 2000 or 1990 from the first column.
If the first column are x's and the second are y's, you will need...

$\sum x_i$ and $\sum x^2_i$ and $\sum y_i$ and $\sum y^2_i$ and $\sum x_iy_i$.
• Apr 4th 2009, 06:11 AM
rose
Thank you for your help but now i am more confussed is there any way you could please break it down for me (Happy)

Thank you

Quote:

Originally Posted by matheagle
The correlation coefficient is the ratio of the covariance over the standard deviations.
In this case it would be smart to subtract off a number like 2000 or 1990 from the first column.
If the first column are x's and the second are y's, you will need...

$\sum x_i$ and $\sum x^2_i$ and $\sum y_i$ and $\sum y^2_i$ and $\sum x_iy_i$.

• Apr 4th 2009, 09:35 PM
matheagle
• Apr 7th 2009, 01:26 AM
rose
x= 19955
y= 18560
x2= 3.9820
y2= 3.9474
• Apr 7th 2009, 01:52 AM
mr fantastic
Quote:

Originally Posted by rose
x= 19955
y= 18560
x2= 3.9820
y2= 3.9474

There's one more sum you need to calculate. Then substitute the sums into the formula given here: Computing Pearson's Correlation Coefficient
• Apr 7th 2009, 06:36 AM
matheagle
Quote:

Originally Posted by rose
x= 19955
y= 18560
x2= 3.9820
y2= 3.9474

I think you're missing some decimal places on those sums of squares.