You are a portfolio investor and, for simplicity, are investing in only two asse
ID: 2796431 • Letter: Y
Question
You are a portfolio investor and, for simplicity, are investing in only two assets. You must invest in one asset(called Asset A) and then choose one additional asset from a choice of 3 assets. The asset you must invest in has a variance of 0.09. Now, you must choose 1 asset from the following 3.
i) asset B has a variance of 0.04 and a correlation of 0.90 with Asset A.
ii) Asset C has a variance of 0.04 and a correlation of 0.45 with Asset A.
iii) Asset D has a standard deviation of 0.25 and a correlation of 0.35 with Asset A.
Assume equal weights in Asset A and the 2nd asset you choose. You are to choose the asset that provides you the lowest portfolio risk. Which asset do you choose?
Explanation / Answer
Portfolio Risk :
Portfolio Variance = w2A*2(RA) + w2B*2(RB) + 2*(wA)*(wB)*(RA)*(RB) * R
Where: wA and wB are portfolio weights, 2(RA) and 2(RB) are variances and R is the correlation
Note that Asset B will not be chosen as Asset C has the same variance but a lower correlation
Thus we do the calculation with C and D to see the best portfolio
1) With Asset C :
Portfolio Variance = 0.52 * 0.09 + 0.52 * 0.04 + 2 * 0.5 * 0.5 * 0.3 * 0.2 * 0.45 = 0.046
2) With Asset D :
Portfolio Variance = 0.52 * 0.09 + 0.52 * 0.0625 + 2 * 0.5 * 0.5 * 0.3 * 0.25 * 0.35 = 0.05125
1) With Asset C :
Portfolio Variance = 0.52 * 0.09 + 0.52 * 0.04 + 2 * 0.5 * 0.5 * 0.3 * 0.2 * 0.45 = 0.046
Clearly it is less with Asset C, thus we chose it.
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