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Unformatted text preview: linear) 4. Existence of strong correlation does not mean that the association is causal , that is change of one variable is caused by the change of the other (it may be third factor that cause s both variables change in the same direction) Computation y x s s n y y x x r ) 1 ( ) )( (= ∑ Where x s = standard deviation of sample x, and s y = standard deviation of sample y Example: x y (x  x ) (y  y ) Product 6 582 16 10 344 16 14 7 19 8 5 1 5 21 12 7 5 35 Sum 70 35 72 Mean 14 7 s 6.20 3.39 2 4 6 8 10 12 14 5 10 15 20 25 856 . 39 . 3 20 . 6 ) 1 5 ( 72 = × ×= r...
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 Summer '08
 dikong
 Statistics, Standard Deviation, Causality, Pearson productmoment correlation coefficient, Correlation does not imply causation

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