MỤC LỤC
PREFACE 2
CHAPTER 1: SOME CONCEPTS OF THE PROBABILITY, EXTREMAL FINITE SET THEORY AND THE ENTROPY FUNCTION
1. Some concepts of the probability
1.1.Probability space
Throughout this book, Ω denotes a non-empty set of interest, called sample space. For example, Ω is the real line, or Ω is the set of all possible outcomes when tossing a fair coin twice.
1.1.1.Algebra and σ-Algebra
Definition:
- Let Ω be a non-empty set. A collection F of subsets of Ω is called a algebra over Ω if
(i) ;
(ii) It is closed under complement:
(iii) It is closed under taking finite union:
- Let Ω be a non-empty set. A collection F of subsets of Ω is called a σ-field (or σ-algebra) over Ω if
(i) ;
(ii) It is closed under complement:
(iii) It is closed under taking countable unions:
1.1.2.Probability measure
Definition:
Let be a function. P is called a probability measure if
(i)
(ii)For every disjoint events then
(iii)
1.2. Independence of events
Definition 1.2.1. Two events A and B are independent if P(AB) = P(A) · P(B).
Proposition1.2.1. Let A and B be events. Let A1 and A2 be events.
1. If A is independent of B, then Ac is independent of B.
2. Suppose and are disjoint. If is independent of B and is independent of B, then is independent of B.
Definition 1.2.2. A finite collection of events {A1, A2, . . . , An} are independent if for every I ⊂ {1, 2, . . . , n} we have
1.3. Random variable and distribution function
Definition 1.3.1. A random variable is a measurable function on a probability space. Usually, random variables are denoted by capital Roman letters. For example,
where µ is the Lesbesgue measure, but it doesn’t really matter. It’s usually Lesbesgue measure. What’s really important is the probability P. For
X is called a random vector.
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