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Product Moment Correlation Coefficient

Hi I'm doing GCSE Level Statistics and i was wondering if somebody cold please describe Product Moment Correlation Coefficient simply step by step. Thanks in Advance.
Reply 1
Avatar for lilman91
lilman91
4
Well this is the way i have learnt it in Statistics 2 A-level. I find this the easiest way to remember.

1) First calculate Sxx. To do this, you work out the mean of all the x-values. Then you square all the x-values and add them up.

Sxx = (Sum of squares of x values) -[ n *(mean of x)² ] (n= number of data points)

2) Then you calculate Syy. This is similar because

Syy = (Sum of squares of y values) - [n * (mean of y)² ]

3) Now you calculate Sxy. To do this, you first need to multiply each x value by the corresponding y value and then add them all up. So example:

(3,4) (6,7): you would do 3*4 + 6*7 = 54 (This is the sum of x*y values)

So Sxy = (Sum of x*y values) - [n* (mean of x) * (mean of y)]

These are the 3 things you need to calculate first so now:

Product Moment correlation coefficient, r = (Sxy)/sqrt(Sxx * Syy)

Hopefully that's a good enough explanation and has helped you.
Reply 2
Avatar for patrick93
patrick93
OP
8
Thanks!
This is a very easy way
Yeah, I used that to do my GCSE Statistics coursework too. I got an A in it :biggrin:

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