While an infinite number of distributions could be constructed to model a discrete random variable, there are only a handful that have found wide applicability to real-world data sets. These quizzes explore the most important discrete distributions, and how to determine which one is a good fit for a given situation:

- Uniform
- Bernoulli
- Binomial
- Geometric
- Poisson

A manufacturer knows that 20% of the widgets he produces are defective. If he needs to sell at least 10 (non-defective) widgets, how many times does he need to produce a (possibly defective) widget so that he has at least a 90% chance of meeting his quota?

A person knows that they average 9 letters in the mail per week. What is the probability that, in a given week, the person receives exactly 9 letters?