Given P(X = 20, Y = 0) = 0.4, and P(X = 30, Y = 50) = 0.6, then COV(XY)is:

CFA Level I
#1

Given P(X = 20, Y = 0) = 0.4, and P(X = 30, Y = 50) = 0.6, then COV(XY)is: A) 125.00. B) 11.18. C) 120.00. D) 25.00. this is another quesion , i need a short cut to it !!! pleaseeeeeeeeee

#2

I’ll say C) 120 E(X)=26, E(Y)=30 Cov(X,Y)=(0.4)(30-0)(26-20)+(0.6)(30-50)(26-30)=120 Is that it?

#3

X bar = 0.4*20+0.6*30=26 Y bar=0.4*0+0.6*50=30 cov=0.4*(20-26)*(0-30)+0.6*(30-26)*(50-30)=120 C

#4

C

#5

C. 120 let me know if its right. thanks

#6

YESSSS, IT IS C, BUT IT TAKE ME SO LONG TO SLOVE IT, I NEED A SHORT CUT IF U KNEW…

#7

the plugging took 45 sec which isn’t that bad