The addition rule for probability

Problem types

• The addition rule
• Show the work: either of two overlapping groups

Builds on

• Unions, intersections, and complements
• Adding and subtracting unlike fractions · Useful idea

  The probability of one event or another adds their probabilities, which are fractions.

Leads to

• Using expected value to compare choices · See it applied

  Mutually exclusive outcomes add, so the probability of a set of outcomes is the sum of their probabilities in an expected value.

• A distribution built from frequencies · See it applied

  Relative frequencies of disjoint results add to 1, as the addition rule requires for probabilities.

• Defining a random variable · See it applied

  The probabilities of all values of a random variable add to 1 because the events are disjoint and cover the sample space.

Related skills

None listed.