Answer: 0.00128

## Explanation To calculate the unbiased sample variance, we use the formula: \[ s^2 = \frac{\sum_{i=1}^{n}(x_i - \bar{x})^2}{n-1} \] Where: - n = sample size = 5 - x_i = individual returns - \bar{x} = sample mean **Step 1: Calculate the mean** \[ \bar{x} = \frac{21 + 17 + 11 + 18 + 15}{5} = \frac{82}{5} = 16.4 \] **Step 2: Calculate squared deviations from mean** \[ (21 - 16.4)^2 = (4.6)^2 = 21.16 \] \[ (17 - 16.4)^2 = (0.6)^2 = 0.36 \] \[ (11 - 16.4)^2 = (-5.4)^2 = 29.16 \] \[ (18 - 16.4)^2 = (1.6)^2 = 2.56 \] \[ (15 - 16.4)^2 = (-1.4)^2 = 1.96 \] **Step 3: Sum of squared deviations** \[ \sum(x_i - \bar{x})^2 = 21.16 + 0.36 + 29.16 + 2.56 + 1.96 = 55.2 \] **Step 4: Calculate unbiased sample variance** \[ s^2 = \frac{55.2}{5-1} = \frac{55.2}{4} = 13.8 \] **Step 5: Convert to decimal form** Since the returns are given in percentages, we need to convert the variance to decimal form: \[ s^2 = \frac{13.8}{100^2} = \frac{13.8}{10000} = 0.00138 \] Therefore, the correct unbiased sample variance is **0.00138**, which corresponds to option B.

Author: LeetQuiz .