Probability Theory Overview
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Questions and Answers

What is the sample space when rolling a single six-sided die?

  • {0, 1, 2, 3, 4, 5, 6}
  • {1, 2, 3, 4, 5, 6} (correct)
  • {1, 2, 3, 4, 5, 6, 7}
  • {1, 2, 3}
  • How is a random experiment defined?

  • An experiment with only one possible outcome.
  • An experiment with multiple sample spaces.
  • An experiment with predictable outcomes.
  • An experiment where outcomes are inherently unknown. (correct)
  • If events A and B are mutually exclusive, what is P(A ∩ B)?

  • P(A) × P(B)
  • P(A) + P(B)
  • 1
  • 0 (correct)
  • What does the classical definition of probability state?

    <p>P(A) = m(A) / n(S)</p> Signup and view all the answers

    Which of the following axioms states that the probability of any event A is at least zero?

    <p>Axiom (i)</p> Signup and view all the answers

    For a certain event S, what is the probability P(S)?

    <p>1</p> Signup and view all the answers

    According to the properties of probability, which statement is true?

    <p>P(Ac) = 1 - P(A)</p> Signup and view all the answers

    What does P(A U B) represent?

    <p>The probability of at least one of A or B occurring.</p> Signup and view all the answers

    What is the probability of event A given that event B occurs?

    <p>P(AB) / P(B)</p> Signup and view all the answers

    If P(A) = 3/8 and P(B) = 5/8, what is P(AB) if A and B are independent events?

    <p>15/64</p> Signup and view all the answers

    What condition must be satisfied for events A and B to be considered independent?

    <p>P(AB) = P(A) * P(B)</p> Signup and view all the answers

    Which of the following is Bayes' theorem expressed mathematically for event X?

    <p>P(Ai|X) = P(Ai) * P(X|Ai) / P(X)</p> Signup and view all the answers

    What is the probability that the second box is chosen if a red ball is drawn?

    <p>20/27</p> Signup and view all the answers

    How many red balls are in the first box?

    <p>3 red balls</p> Signup and view all the answers

    What role does the concept of mutually exclusive events play in probability theory?

    <p>They cannot occur at the same time.</p> Signup and view all the answers

    If three boxes contain different amounts of red and white balls, what is a necessary step in calculating the probability of choosing a specific color?

    <p>Use the individual probabilities from each box.</p> Signup and view all the answers

    Which formula correctly represents the addition of two events A and B when they are not mutually exclusive?

    <p>P(A + B) = P(A) + P(B) - P(AB)</p> Signup and view all the answers

    What is the conditional probability notation for event B given that event A has occurred?

    <p>P(B | A)</p> Signup and view all the answers

    If events A and B are independent, what is true about their joint probability P(AB)?

    <p>P(AB) = P(A)P(B)</p> Signup and view all the answers

    In the probability example about selecting watches, how many ways can 2 defective watches be chosen from 3 defective ones?

    <p>6</p> Signup and view all the answers

    Which scenario correctly depicts when at least one selected watch is defective from a pack of 10?

    <p>One watch is defective and the other is non-defective.</p> Signup and view all the answers

    How many complete weeks are there in a leap year?

    <p>52</p> Signup and view all the answers

    What is the method to determine the probability that a leap year contains 53 Sundays?

    <p>Calculate favorable outcomes with selected day pairs.</p> Signup and view all the answers

    What is the probability that at least one of two randomly selected watches from a pack of 10 is defective, given that there are 3 defective watches?

    <p>$\frac{8}{15}$</p> Signup and view all the answers

    What is the probability of choosing the first box, A1?

    <p>1/3</p> Signup and view all the answers

    What is the probability P(X | A1) of drawing a red ball given that box A1 is chosen?

    <p>3/5</p> Signup and view all the answers

    According to Bayes' Theorem, what does P(A2 | X) represent?

    <p>Probability of choosing box A2 after drawing a red ball</p> Signup and view all the answers

    If E(x) represents the mathematical expectation of a random variable, what does Var(x) represent?

    <p>Variance of the values around the mean</p> Signup and view all the answers

    What is the probability of drawing an ace from one deck of cards?

    <p>1/13</p> Signup and view all the answers

    What is the relationship between events A and B in terms of independence?

    <p>They are independent events</p> Signup and view all the answers

    How do you calculate the overall probability P(X)?

    <p>P(A1) * P(X | A1) + P(A2) * P(X | A2) + P(A3) * P(X | A3)</p> Signup and view all the answers

    What is the mathematical expectation (mean) defined as?

    <p>The weighted sum of outcomes based on their probabilities</p> Signup and view all the answers

    Study Notes

    Probability Theory

    • Sample space: The set of all possible outcomes of a random experiment.
    • Event: A subset of the sample space.
    • Mutually exclusive events: Two events that cannot occur simultaneously.

    Classical Definition of Probability

    • Probability of an event: The ratio of the number of favorable outcomes to the total number of possible outcomes.
    • Formula: P(A) = m(A) / n(S), where m(A) is the number of favorable outcomes and n(S) is the total number of outcomes.

    Axioms of Probability

    • Axiom 1: For any event A, P(A) ≥ 0.
    • Axiom 2: For the certain event S, P(S) = 1.
    • Axiom 3: For mutually exclusive events A1, A2, ... , An, P(A1 U A2 U ... U An) = P(A1) + P(A2) + ... + P(An).

    Notations

    • P(A): Probability of occurrence of event A.
    • P(Ac) or P(Ā): Probability of non-occurrence of event A.
    • P(AUB) or P(A+B): Probability of occurrence of at least one of events A and B.
    • P(A∩ B) or P(AB): Probability of occurrence of both A and B.
    • P(A/B): Probability of occurrence of event A given that B has already occurred.

    Properties of Probability

    • P(φ) = 0: The probability of the impossible event is zero.
    • P(A) ≤ 1: The probability of any event is less than or equal to 1.
    • P(Ac) = 1 − P (A): The probability of an event not occurring is 1 minus the probability of the event occurring.
    • P( B ∩ Ac) = P (B) − P (B ∩ A): The probability of event B occurring and event A not occurring is the probability of B minus the probability of both happening.

    Theorem of Addition

    • For two events: P(A + B) = P(A) + P(B) – P(AB)
    • For three events: P(A + B + C) = P(A) + P(B) + P(C) – P(BC) – P(CA) – P(AB) + P(ABC)

    Conditional Probability

    • Formula: P(B/A) = P(AB) / P(A)

    Theorem of Compound Probability

    • Formula: P(AB) = P(A).P(B/A)

    Independent Events

    • Definition: Two events A and B are independent if and only if P(AB) = P(A)P(B).

    Bayes' Theorem

    • Formula: P(Ai/X) = [P(Ai)P(X/Ai)] / Σ[P(Aj)P(X/Aj)], where i = 1, 2, ... , n

    Mathematical Expectation

    • Formula: E(x) = Σpixi, where x is a variable, xi are the values of x, and pi are the corresponding probabilities.
    • Variance: Var(x) = E(x2) – [E(x)]2

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    Description

    This quiz covers fundamental concepts of probability theory, including the definitions of sample space, events, and mutually exclusive events. You'll explore classical probability definitions, axioms, and important notations used in probability. Test your understanding of these essential concepts.

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