"The **68-95-99.7 rule**, also known as the **empirical rule**, in statistics states that for a normal distribution, approximately 68% of the data falls within one standard deviation of the mean (or expected return in this context). This means there's a 68% probability that an observed value will be within one standard deviation away from the expected return. **Keywords:** confidence level, standard deviation, expected return, normal distribution, 68-95-99.7 rule, empirical rule, probability".