Random signals can be either deterministic or random, depending on their source and characteristics. Deterministic signals have predictable properties, while random signals have unpredictable properties that require statistical analysis. Examples of random signals include thermal noise from electron movement and periodic signals with random parameters like phase or amplitude. Random variables are values that depend on the outcome of a random experiment. A random variable is a function that assigns a numerical value to each possible outcome in the sample space of an experiment. For example, in a coin toss experiment repeated 20 times, the number of heads obtained is a random variable that can take on values from 0 to 20.