Calculate the sample correlation between test score and assembly time.

Test Score Assembly Time

(minutes)

(x) (y)

40 16

50 14

60 12

75 10

80 8

85 10

90 7

-----------------------------------

540 77

MY WORK:

X^2=1600,2500,3600,5625,6400,7225,8100=35050

y^2=256,196,144,100,64,100,49=909

X*Y=640,700,720,750,640,850,630=4930

ss(xy)=4930-(540*77/7)=-1010

ss(x)=35050-(291600/7)=-6607.142

ss(y)=909-(5929/7)=62

Correlation Coefficient is:

r=-1010/(square root of -6607.142 * 62)=???????

This is where i get stuck. Everytime i try to calculate the answer i come up with an error. Can someone pls tell me if i did this correctly. I cant seem to get the answer to the coefficient