Math Problem Statement

Asset X has a standard deviation of 15%, and Asset Y has a standard deviation of 20%.The correlation coefficient between asset X and y is 0.3. The portfolio weights of X is 50 % and y is 50%. Estimate the portfolio standard deviation. a. 16.82% b. 17.32% c. 18.42% d. 19.02%

Solution

The standard deviation of a two-asset portfolio is given by the formula:

σp=wX2σX2+wY2σY2+2wXwYρXYσXσY\sigma_p = \sqrt{w_X^2 \sigma_X^2 + w_Y^2 \sigma_Y^2 + 2 w_X w_Y \rho_{XY} \sigma_X \sigma_Y}

where:

  • wX=0.5w_X = 0.5, wY=0.5w_Y = 0.5 (portfolio weights)
  • σX=15%=0.15\sigma_X = 15\% = 0.15 (standard deviation of Asset X)
  • σY=20%=0.20\sigma_Y = 20\% = 0.20 (standard deviation of Asset Y)
  • ρXY=0.3\rho_{XY} = 0.3 (correlation coefficient)

Step-by-step Calculation:

  1. Compute the squared terms:

(0.5)2(0.15)2=0.52×0.0225=0.25×0.0225=0.005625(0.5)^2 (0.15)^2 = 0.5^2 \times 0.0225 = 0.25 \times 0.0225 = 0.005625

(0.5)2(0.20)2=0.52×0.04=0.25×0.04=0.01(0.5)^2 (0.20)^2 = 0.5^2 \times 0.04 = 0.25 \times 0.04 = 0.01

  1. Compute the interaction term:

2(0.5)(0.5)(0.3)(0.15)(0.20)=2×0.25×0.3×0.15×0.202 (0.5)(0.5)(0.3)(0.15)(0.20) = 2 \times 0.25 \times 0.3 \times 0.15 \times 0.20

=0.5×0.3×0.15×0.20=0.5×0.009=0.0045= 0.5 \times 0.3 \times 0.15 \times 0.20 = 0.5 \times 0.009 = 0.0045

  1. Sum up all terms:

0.005625+0.01+0.0045=0.0201250.005625 + 0.01 + 0.0045 = 0.020125

  1. Take the square root:

σp=0.0201250.142\sigma_p = \sqrt{0.020125} \approx 0.142

σp=14.2%\sigma_p = 14.2\%

Since none of the options match, let's recheck the calculations carefully in Python to ensure accuracy. math

Given data

w_X = 0.5 w_Y = 0.5 sigma_X = 0.15 sigma_Y = 0.20 rho_XY = 0.3

Portfolio standard deviation formula

sigma_p_squared = (w_X2 * sigma_X2) + (w_Y2 * sigma_Y2) + (2 * w_X * w_Y * rho_XY * sigma_X * sigma_Y) sigma_p = math.sqrt(sigma_p_squared)

Convert to percentage

sigma_p * 100The calculated portfolio standard deviation is approximately 14.19%, which does not match any of the provided answer choices. There may be an issue with the given options or a mistake in interpretation. Let me know if you need further verification or explanation.

Related Questions:

  1. How does correlation affect portfolio risk?
  2. What happens to portfolio standard deviation when correlation is -1?
  3. How do you compute the standard deviation for a three-asset portfolio?
  4. Why is diversification important in portfolio management?
  5. How does increasing the weight of a lower-risk asset affect portfolio risk?

Tip: A lower correlation between assets generally reduces portfolio risk due to diversification benefits.

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Math Problem Analysis

Mathematical Concepts

Portfolio Theory
Standard Deviation
Correlation
Asset Management

Formulas

Portfolio Standard Deviation Formula: σp = √(wX² * σX² + wY² * σY² + 2 * wX * wY * ρXY * σX * σY)

Theorems

Portfolio Risk and Diversification

Suitable Grade Level

Grades 11-12