5.20. Use the definition (5.15) of the probability of an event to prove the following basic facts about probability theory. (a) Let E and F be disjoint events. Then Pr(EU F) = Pr(E) + Pr(F). (b) Let E and F be events that need not be disjoint. Then Pr(EU F) = Pr(E) + Pr(F) − Pr(E^ F). (c) Let E be an event. Then Pr(Ec) = 1 − Pr(E). (d) Let E1, E2, E3 be events. Prove that Pr(E₁ ¯ E2 ¯ E3) = Pr(E₁) + Pr(E2) + Pr(E3) − Pr(E₁ ^ E₂) – Pr(E₁ ^ E3) — Pr(E2 ^ E3) + Pr(E₁ ^ E2 ^ E3). The formulas in (b) and (d) and their generalization to n events are known as the inclusion-exclusion principle.

A First Course in Probability (10th Edition)
10th Edition
ISBN:9780134753119
Author:Sheldon Ross
Publisher:Sheldon Ross
Chapter1: Combinatorial Analysis
Section: Chapter Questions
Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...
icon
Related questions
Question

[Algebraic Cryptography] How do you solve this? The second picture is definitions

5.20. Use the definition (5.15) of the probability of an event to prove the
following basic facts about probability theory.
(a) Let E and F be disjoint events. Then
Pr(EU F) = Pr(E) + Pr(F).
(b) Let E and F be events that need not be disjoint. Then
Pr(EUF) = Pr(E) + Pr(F) − Pr(E^F).
(c) Let E be an event. Then Pr(Ec) = 1 − Pr(E).
(d) Let E1, E2, E3 be events. Prove that
Pr(E₁ U E2 U E3) = Pr(E₁) + Pr(E2) + Pr(E3) — Pr(E₁ ^ E₂)
– Pr(E₁ E3) — Pr(E2 ~ E3) + Pr(E₁ E₂ E3).
The formulas in (b) and (d) and their generalization to n events are known
as the inclusion-exclusion principle.
Transcribed Image Text:5.20. Use the definition (5.15) of the probability of an event to prove the following basic facts about probability theory. (a) Let E and F be disjoint events. Then Pr(EU F) = Pr(E) + Pr(F). (b) Let E and F be events that need not be disjoint. Then Pr(EUF) = Pr(E) + Pr(F) − Pr(E^F). (c) Let E be an event. Then Pr(Ec) = 1 − Pr(E). (d) Let E1, E2, E3 be events. Prove that Pr(E₁ U E2 U E3) = Pr(E₁) + Pr(E2) + Pr(E3) — Pr(E₁ ^ E₂) – Pr(E₁ E3) — Pr(E2 ~ E3) + Pr(E₁ E₂ E3). The formulas in (b) and (d) and their generalization to n events are known as the inclusion-exclusion principle.
Definition. A sample space (or set of outcomes) is a finite⁹ set . Each
outcome we is assigned a probability Pr(w), where we require that the
probability function
Pr : Ω
satisfy the following two properties:
(a) 0≤ Pr(w) ≤ 1 for all w EN and (b) Σ Pr(ω) = 1. (5.14)
WEN
R
Notice that (5.14) (a) corresponds to our intuition that every outcome
has a probability between 0 (if it never occurs) and 1 (if it always occurs),
while (5.14) (b) says that some outcome must occur, so contains all possible
outcomes for the experiment.
Definition. An event is any subset of 2. We assign a probability to an event
ECN by setting
(5.15)
Pr(E) = Σ Pr(w).
WEE
In particular, Pr(Ø) = 0 by convention, and Pr(N) = 1 from (5.14)(b).
Transcribed Image Text:Definition. A sample space (or set of outcomes) is a finite⁹ set . Each outcome we is assigned a probability Pr(w), where we require that the probability function Pr : Ω satisfy the following two properties: (a) 0≤ Pr(w) ≤ 1 for all w EN and (b) Σ Pr(ω) = 1. (5.14) WEN R Notice that (5.14) (a) corresponds to our intuition that every outcome has a probability between 0 (if it never occurs) and 1 (if it always occurs), while (5.14) (b) says that some outcome must occur, so contains all possible outcomes for the experiment. Definition. An event is any subset of 2. We assign a probability to an event ECN by setting (5.15) Pr(E) = Σ Pr(w). WEE In particular, Pr(Ø) = 0 by convention, and Pr(N) = 1 from (5.14)(b).
Expert Solution
steps

Step by step

Solved in 2 steps with 1 images

Blurred answer