Definition of complete groups of events:A complete group of events is a group of incompatible events, such that at least one of them must occur as a result of an experiment.
Example 1:Tossing a coin twice will result in the following four events: (T, T), (T, H), (H, T), (H, H).
Obviously, all events are mutually incompatible, only one of them can occur as a result of an experiment "tossing a coin twice."
In flipping a coin n times, the following events: "No heads and n tails are an outcome of n trials, " "One head and n â?' 1 tails are an outcome of n trials, " "Two heads and n â?' 2 tails are an outcome of n trials, " ..., "n â?' 1 heads and one tail are an outcome of n trials," "n heads are an otucome of n trials" form a complete group of events.
An example is rolling a fair die, where the possible events for one trial are the numbers which show up on the die, i.e. ...
We give an example of a random procedure (tossing a fair die), in which we identify the possible outcomes (events) as well as their probabilities.