Probability and Random Variables Quiz
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Questions and Answers

What is the value of 𝑃(𝐴|𝐵) if 𝑃(𝐴) = 1/4, 𝑃(𝐵) = 1/3, and 𝑃(𝐴 ∪ 𝐵) = 1/2?

  • 1/6
  • 1/12 (correct)
  • 1/3
  • 1/4
  • What is the probability of an impossible event?

  • 1/4
  • 1/2
  • 1
  • 0 (correct)
  • For the probability density function 𝑓(𝑥) = 𝑘𝑥, where 0 < 𝑥 < 1, what is the value of k?

  • 1 (correct)
  • 2
  • 0
  • 3
  • If the discrete random variable X has values (0, 𝑘), (1, 2𝑘), (2, 3𝑘), (3, 4𝑘), what is the value of k?

    <p>0.1</p> Signup and view all the answers

    If events A and B are mutually exclusive, what is the probability P(A|B)?

    <p>0</p> Signup and view all the answers

    What is the formula for Cov(aX, bY) when X and Y are random variables?

    <p>abCov(X,Y)</p> Signup and view all the answers

    If X and Y are independent random variables, what is the value of Cov(X,Y)?

    <p>0</p> Signup and view all the answers

    What is the mean of a binomial distribution with parameters n and p?

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

    The variance of a binomial distribution is given by which of the following formulas?

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

    What is the standard deviation of a binomial distribution with parameters n and p?

    <p>√npq</p> Signup and view all the answers

    What is the probability of getting exactly 3 heads when tossing 6 coins?

    <p>0.2325</p> Signup and view all the answers

    Which distribution is considered the limiting case of the binomial distribution?

    <p>Poisson distribution</p> Signup and view all the answers

    For a standard normal distribution, what is the mean?

    <p>0</p> Signup and view all the answers

    What is the standard deviation of a Poisson distribution with parameters n=10000 and p=0.001?

    <p>3.1622</p> Signup and view all the answers

    If α = 1/3 in an exponential distribution, what is the mean?

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

    What is the variance of an exponential distribution when α = 1/2?

    <p>1/4</p> Signup and view all the answers

    What is the variance of a Poisson distribution with parameter λ = 2?

    <p>2</p> Signup and view all the answers

    In a Poisson distribution, if 2P(X = 1) = P(X = 2), what is the variance?

    <p>2</p> Signup and view all the answers

    If P(X = 2) = P(X = 3) in a Poisson distribution, what is P(X = 0)?

    <p>e^-3</p> Signup and view all the answers

    In a binomial distribution, which characteristic does NOT apply?

    <p>Each trial results in two or more outcomes.</p> Signup and view all the answers

    What is the relationship between the mean and variance in a binomial distribution when p = 0.5?

    <p>They are only equal when p = 0.5.</p> Signup and view all the answers

    What is the variance of the expression $V(19-4X)$ if $V(X) = 7.15$?

    <p>114.4</p> Signup and view all the answers

    Given $E[X] = 3$ and $E[X^2] = 10$, what is the variance $V(X)$?

    <p>7</p> Signup and view all the answers

    If $E[X] = 2$ and $E[X^2] = 12$, what is the standard deviation of $X$?

    <p>3.1622</p> Signup and view all the answers

    If $V(X) = 15$, what is the variance of the expression $V(8X)$?

    <p>120</p> Signup and view all the answers

    If $A$ and $B$ are mutually exclusive events, what is $P(A igcap B)$?

    <p>0</p> Signup and view all the answers

    Given that $E[X] = 3$ and $V[X] = 18$, what is $E[X^2]$?

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

    If $X$ and $Y$ are independent random variables, what is $E(XY)$?

    <p>E(X)E(Y)</p> Signup and view all the answers

    What is the marginal distribution of $X$ given the joint pdf $f(x, y) = e^{-(x + y)}$ for $0 < x, y < ∞$?

    <p>e^{-x}</p> Signup and view all the answers

    Study Notes

    Probability and Random Variables

    • Conditional probability: If P(A) = 1/4, P(B) = 1/3, P(A ∪ B) = 1/2, then P(A|B) = 1/6
    • Probability of an impossible event is zero.
    • Probability density function (pdf) of a random variable X is f(x) = kx for 0 < x < 1, then k = 2.
    • Discrete random variable X with values (0, 1, 2, 3) and probabilities (k, 2k, 3k, 4k) has k = 0.1.
    • For events A and B, if P(A) = 0.4, P(B) = 0.04, and P(A ∩ B) = 0.01, then P(A|B) = 0.25
    • Mutually exclusive events A and B have P(A ∩ B) = 0.
    • Independent events A and B have P(A|B) = P(A).
    • If V(X) = 7.15, then V(19 - 4X) = 114.4
    • If E[X] = 3 and E[X²] = 10, then V(X) = 7.

    Other Statistical Concepts

    • If E[X] = 2, E[X²] = 12, then the standard deviation is 2.8284.

    • If V(X)= 15, then V(8X) is 960

    • If E[X]= 3 , V(X) is 18 then E(X^2) is 27

    • If P(0 < X < 0.5) and pdf of random variable is 2x, 0<x<1, is 0.25

    • The mean of a binomial distribution is np; If n = 10000, p = 0.001, then standard deviation is 3.1622.

    • Mean of exponential distribution with a = 1/3 is 3

    • Variance of exponential distribution with a = 1/2 is 4.

    • Variance of a Poisson distribution with parameter λ = 2 is 2

    • In Poisson distribution, if 2P(X = 1) = P(X = 2), then variance is 2

    • Standard deviation of binomial distribution is √npq

    • Probability of getting exactly 3 heads with 6 coins is 0.3125

    • The moment generating function of uniform distribution is ((e^(at) - e^(-at))/a.

    Expected Values

    • If X and Y are independent random variables, then E(XY) = E(X)E(Y).
    • If the marginal distribution of X is given as (0, 0.4), (1, 0.2), (2, 0.1), (3, 0.3), then E(X) = 1.3 and E[X²]=1.7
    • If the joint pdf of X and Y is e^(x+y),0<x,y<∞ ,then marginal distribution of X = ex

    Additional Concepts

    • The mean of Poisson distribution equals the mean of the exponential distribution when λ = a = 1
    • The exponential distribution is defined over the interval [0, ∞].
    • Binomial distribution has equal mean and variance only when p = 0.5).
    • If X ~ N(5, 32), then P(X < 8) is equals to P(Z < 0.5303)..
    • Standard normal distribution has a mean of 0, and a variance of 1, and a standard deviation of 1,
    • Variance of a uniform distribution is (b-a)^2/12.
    • If X is a sample mean and μ is the population mean, then E(X) = μ.
    • Variance of sampling distribution of sample means is σ²/n, where σ is the population standard deviation and n is the sample size.
    • If x is a normal variate and X/σ = Y+6 where Y~N(0,1) then mean and variance of x are 6 and 4, respectively.
    • Correlation coefficients lies between -1 and 1

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    Description

    Test your knowledge on key concepts of probability and random variables, including conditional probability, probability density functions, and properties of discrete random variables. This quiz covers essential calculations and theoretical understandings needed for mastering the subject.

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