# can anyone do COVAR?

Re: Covarience new Posted by: amrcd1 (IP Logged) [hide posts from this user] Date: May 31, 2008 08:33AM 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 shprt cut to it !!! pleaseeeeeeeeee

Didn’t you post this already today No advice on quick calcs… its a long find the mean, the individual deviations, etc etc calc. Answer to this on is C.

can somebody explain how to interpret this cryptogram? I have seen covar data only in table format.

You easily put it in table format. S1 = .4 X = 20 Y =0 S2 = .6 X = 30 Y = 50 Let me try to attempt to solve this to see if I know it. E(x) = 20*.4 + 30*.6 = 26 E(y) = 50*.6 = 30 Cov(x,y) = Sum(Pi) [(xi - e(x))(yi-e(y))] you get .4*(-6*-30) + .6(4*20) = 120 what’s the answeR?

This isn’t diffcult… Remember, Correlation (x,y aka Beta) = Covar(x,y)/St Dev x * St Dev y Now plug the x and y numbers on your calculator (BA II Plus is what I have) The calculator gives you: r= beta yand standard dev for x & y now solve for CoVAR using the equation above and you get your answer… Answer=125

You can’t use the calculator on this one to calculate COVAR. It gives you 125 when the answer is 120.

You can’t put the probability weights in the calc, correct? Also, calc give corr value… does it also do cov?

Right. If the weighting is equal, you can calculate COV easily from the calc because it gives you the correlation ® and the two standard deviations.

mcf Wrote: ------------------------------------------------------- > You can’t put the probability weights in the calc, > correct? > > Also, calculator give corr value… does it also do cov? Oops sorry guys, didn’t even look at the weights. No the BAII doesn’t give COVAR but it gives correlation coeff & Standard Deviations.

I can do it…I always fukc it up when I’m not under exam pressure, ha ha.