Final answer:
To find the standard deviation (σ) of a random variable x, you need to calculate the variance (σ²) first. The variance is found by summing the squared deviations from the expected value. Finally, take the square root of the variance to find the standard deviation.
Step-by-step explanation:
The standard deviation (σ) of a random variable x can be found by taking the square root of the variance (σ²). To calculate the variance of a discrete random variable, you need to find each deviation from its expected value, square it, multiply it by its probability, and add the products. Then, take the square root of the variance to find the standard deviation.