This unit focuses on two critical families of probability distributions for discrete random variables: Binomial and Geometric. Students will learn to identify the specific conditions required for each—often remembered by the mnemonics BINS (Binary, Independent, Number of trials, Success probability) for binomial and BITS (Binary, Independent, Trials until success, Success probability) for geometric.

Key topics include calculating probabilities for a specific number of successes using the binomial probability formula and finding the "waiting time" for the first success using the geometric probability formula. Students will also calculate and interpret the mean (expected value) and standard deviation for both distributions. Finally, the chapter introduces the Normal approximation to the binomial distribution, exploring when it is appropriate to use a Normal curve to estimate binomial probabilities using the Large Counts Condition (np ≥ 10 and n(1-p) ≥ 10).