Читать книгу Probability and Statistical Inference - Robert Bartoszynski - Страница 27

Consider two tosses of a coin, and the corresponding sample space consisting of four outcomes: HH, HT, TH, and TT. The event “heads in the first toss” HH, HT} is contained in the event “at least one head” HH, HT, TH}. The events “the results alternate” and “at least one head and one tail” imply one another, and hence are equal.

Definition 1.3.3 The set containing no elements is called the empty set and is denoted by . The event corresponding to is called a null (impossible) event.