The Practice of Statistics 4e - Ch 5 Vocab

Complement of an event AC

Refers to the event "not A

Complement rule

The probability rule that an event does not occur is 1 minus the probability that the event does occur.

Conditional probability

The probability that one event happens given that another event is already known to have happened.


Any collection of outcomes from some chance process.

General addition rule

If A and B are any two events resulting from some chance process, then the probability that event A or event B (or both) occur is P(A) + P(B) - P(A ? B) .

General multiplication rule

The probability that events A and B both occur can be found using the formula P(A ? B) = P(A) ? P(B | A)

Independent events

Occurrence of one event has no effect on the chance the other event will happen. In other words, if P(A | B) = P(A).


Denoted by A ? B, refers to the situation when both events occur at the same time.

Law of Large Numbers

If we observe more and more repetitions of any chance process, the proportion of times that a specific outcome occurs approaches a single value, which we call the probability of that outcome.

Mutually exclusive (disjoint)

Two events have no outcomes in common and so can never occur together.


A number between 0 and 1 that describes the proportion of times the outcome would occur in a very long series of repetitions.

Probability model

A description of some chance process that consists of two parts: a sample space S and a probability for each outcome.

Sample space S

The set of all possible outcomes of a chance process.


The imitation of chance behavior, based on a model that accurately reflects the situation.

Tree diagram

Used to display the sample space for a chance process that involves a sequence of outcomes.


Denoted by A ? B, consists of all outcomes in A, or B, or both.