Weather picnic probability tree

This probability tree models a plan that changes with the weather. It first separates the possible weather conditions, then assigns different chances to cancelling or holding the picnic after each condition. That second set of probabilities is conditional: the chance of cancelling is higher when it rains. The tree makes this dependence easier to read than a sentence or a table. It can be adapted for contingency planning, weather-sensitive events, or classroom exercises in conditional probability. To calculate a final outcome, multiply the branch probabilities from the first event through the second event. It gives readers a concise reference they can reuse when discussing the result with colleagues.