Probability distributions

A probability distribution describes how likely each possible value is. A handful cover most of what you will meet. Bernoulli is one yes or no outcome, like a single coin flip.

Binomial counts successes in n tries. Poisson counts events per interval, such as orders per hour. Uniform gives every value the same chance.

In the normal distribution, the familiar bell curve, about 68% of values fall within one standard deviation of the mean and 95% within two. Knowing your data's shape guides later choices. A variable with a long right tail, like income, often behaves better after a log transform, and a regression loss quietly assumes something about the errors.