can anyone do COVAR?

[daj224]

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

 

[mcf]

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.

 

[saurya_s]

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

 

[pepp]

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 = 50*.6 = 30

Cov(x,y) = Sum(Pi) [ (xi - e(x))(yi-e)]
you get

.4*(-6*-30) + .6(4*20) = 120

what's the answeR?

 

[kenanadu]

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

 

[SirViper]

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

 

[mcf]

You can't put the probability weights in the calc, correct?

Also, calc give corr value... does it also do cov?

 

[SirViper]

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

 

[kenanadu]

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.

 

[Gouman]

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