Given the probability distribution for assets $X$ and $Y$, we need to compute the expected rate of return, variance, standard deviation, and coefficient of variation for each asset. Then, we need to determine which asset is a better investment.

Probability and StatisticsExpected ValueVarianceStandard DeviationCoefficient of VariationProbability DistributionFinancial Mathematics
2025/6/17

1. Problem Description

Given the probability distribution for assets XX and YY, we need to compute the expected rate of return, variance, standard deviation, and coefficient of variation for each asset. Then, we need to determine which asset is a better investment.

2. Solution Steps

Asset X:
Returns: 8%, 9%, 11%, 12%
Probabilities: 0.10, 0.20, 0.30, 0.40
Expected Return:
E(X)=(0.08)(0.10)+(0.09)(0.20)+(0.11)(0.30)+(0.12)(0.40)E(X) = (0.08)(0.10) + (0.09)(0.20) + (0.11)(0.30) + (0.12)(0.40)
E(X)=0.008+0.018+0.033+0.048=0.107E(X) = 0.008 + 0.018 + 0.033 + 0.048 = 0.107
E(X)=10.7%E(X) = 10.7\%
Variance:
Var(X)=[xiE(X)]2P(xi)Var(X) = \sum [x_i - E(X)]^2 * P(x_i)
Var(X)=(0.080.107)2(0.10)+(0.090.107)2(0.20)+(0.110.107)2(0.30)+(0.120.107)2(0.40)Var(X) = (0.08 - 0.107)^2(0.10) + (0.09 - 0.107)^2(0.20) + (0.11 - 0.107)^2(0.30) + (0.12 - 0.107)^2(0.40)
Var(X)=(0.027)2(0.10)+(0.017)2(0.20)+(0.003)2(0.30)+(0.013)2(0.40)Var(X) = (-0.027)^2(0.10) + (-0.017)^2(0.20) + (0.003)^2(0.30) + (0.013)^2(0.40)
Var(X)=(0.000729)(0.10)+(0.000289)(0.20)+(0.000009)(0.30)+(0.000169)(0.40)Var(X) = (0.000729)(0.10) + (0.000289)(0.20) + (0.000009)(0.30) + (0.000169)(0.40)
Var(X)=0.0000729+0.0000578+0.0000027+0.0000676=0.000201Var(X) = 0.0000729 + 0.0000578 + 0.0000027 + 0.0000676 = 0.000201
Standard Deviation:
SD(X)=Var(X)=0.0002010.014177SD(X) = \sqrt{Var(X)} = \sqrt{0.000201} \approx 0.014177
SD(X)1.42%SD(X) \approx 1.42\%
Coefficient of Variation:
CV(X)=SD(X)E(X)=0.0141770.1070.1325CV(X) = \frac{SD(X)}{E(X)} = \frac{0.014177}{0.107} \approx 0.1325 or 13.25%
Asset Y:
Returns: 10%, 11%, 12%
Probabilities: 0.25, 0.35, 0.40
Expected Return:
E(Y)=(0.10)(0.25)+(0.11)(0.35)+(0.12)(0.40)E(Y) = (0.10)(0.25) + (0.11)(0.35) + (0.12)(0.40)
E(Y)=0.025+0.0385+0.048=0.1115E(Y) = 0.025 + 0.0385 + 0.048 = 0.1115
E(Y)=11.15%E(Y) = 11.15\%
Variance:
Var(Y)=[yiE(Y)]2P(yi)Var(Y) = \sum [y_i - E(Y)]^2 * P(y_i)
Var(Y)=(0.100.1115)2(0.25)+(0.110.1115)2(0.35)+(0.120.1115)2(0.40)Var(Y) = (0.10 - 0.1115)^2(0.25) + (0.11 - 0.1115)^2(0.35) + (0.12 - 0.1115)^2(0.40)
Var(Y)=(0.0115)2(0.25)+(0.0015)2(0.35)+(0.0085)2(0.40)Var(Y) = (-0.0115)^2(0.25) + (-0.0015)^2(0.35) + (0.0085)^2(0.40)
Var(Y)=(0.00013225)(0.25)+(0.00000225)(0.35)+(0.00007225)(0.40)Var(Y) = (0.00013225)(0.25) + (0.00000225)(0.35) + (0.00007225)(0.40)
Var(Y)=0.0000330625+0.0000007875+0.0000289=0.00006275Var(Y) = 0.0000330625 + 0.0000007875 + 0.0000289 = 0.00006275
Standard Deviation:
SD(Y)=Var(Y)=0.000062750.007921SD(Y) = \sqrt{Var(Y)} = \sqrt{0.00006275} \approx 0.007921
SD(Y)0.79%SD(Y) \approx 0.79\%
Coefficient of Variation:
CV(Y)=SD(Y)E(Y)=0.0079210.11150.0710CV(Y) = \frac{SD(Y)}{E(Y)} = \frac{0.007921}{0.1115} \approx 0.0710 or 7.10%
Comparing the Coefficient of Variation:
CV(X)=13.25%CV(X) = 13.25\%
CV(Y)=7.10%CV(Y) = 7.10\%
Since the coefficient of variation of asset Y is lower than asset X, asset Y is a better investment because it has lower relative risk compared to its expected return.

3. Final Answer

Asset X:
Expected Return = 10.7%
Variance = 0.000201
Standard Deviation = 1.42%
Coefficient of Variation = 13.25%
Asset Y:
Expected Return = 11.15%
Variance = 0.00006275
Standard Deviation = 0.79%
Coefficient of Variation = 7.10%
Asset Y is a better investment.

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