Probability Distributions Quiz
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Questions and Answers

What is the mean of a hyper-geometric variable represented as?

  • $E(X) = np$ (correct)
  • $E(X) = N/n$
  • $E(X) = pq$
  • $E(X) = n(N - n)$
  • The variance of a hyper-geometric variable can be calculated using the formula $Var(X) = npq \cdot \frac{N - n}{N - 1}$.

    True

    In a lot containing 30 items, 6 are defective. What is the probability of selecting a random sample of five items containing no defective items?

    0.4783

    The expected value of the number of red chips drawn when taking two chips out of a bowl containing six red and four blue chips is ______.

    <p>1.2</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Mean = The average of a probability distribution Variance = A measure of the dispersion of a probability distribution Hyper-geometric Distribution = Models scenarios without replacement Geometric Distribution = Models scenarios with independent trials</p> Signup and view all the answers

    What type of random variable is used to calculate the probability of getting the first success on a specific trial?

    <p>Geometric random variable</p> Signup and view all the answers

    The hypergeometric distribution deals with sampling with replacement.

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

    What is the probability that the 10th person you encounter in a town with 4% teachers is a teacher?

    <p>0.0031</p> Signup and view all the answers

    The mean of a geometric distribution with probability of success $p$ is _____

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

    Match the terms with their definitions:

    <p>Geometric Distribution = The probability of the first success on trial k Hypergeometric Distribution = Sampling without replacement from a finite population Mean = The average of a probability distribution Variance = A measure of the dispersion of a probability distribution</p> Signup and view all the answers

    If 2% of tires produced by a company are defective, what is the probability that the first defect is found in the first 5 samples?

    <p>0.9171</p> Signup and view all the answers

    The variance of a geometric distribution with probability $p$ is calculated as $p/(1-p)^2$.

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

    What would you expect the number of tires to test until the first defective one is found if 2% of tires are defective?

    <p>50</p> Signup and view all the answers

    What does a geometric random variable represent in probability theory?

    <p>The number of trials until the first success</p> Signup and view all the answers

    The probability of needing x trials for the first success in a geometric distribution decreases as x increases.

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

    Define a geometric random variable.

    <p>A geometric random variable is the number of trials required to get the first success in a Bernoulli process.</p> Signup and view all the answers

    In a geometric distribution, the probability of success on each trial is denoted by ______.

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

    If a fair coin is tossed until a head appears, what is the probability that exactly three tosses are needed?

    <p>1/8</p> Signup and view all the answers

    In the scenario of rolling a die until a six appears, the probability of needing at least 3 rolls is higher than needing at most 4 rolls.

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

    What is the formula to calculate the probability that at most x trials are needed for the first success in a geometric distribution?

    <p>P(X ≤ x) = P(X = 1) + P(X = 2) + ... + P(X = x)</p> Signup and view all the answers

    Match the following scenarios with their corresponding probabilities:

    <p>Tossing a coin, getting a head on the first toss = P = p First success occurs on the third trial after two failures = P = (1-p)²p At least one head in three tosses = 1 - P(X = 0) Rolling a die and getting a six = P = p</p> Signup and view all the answers

    Study Notes

    Probability Distributions

    • Geometric Random Variable: A Bernoulli trial is repeated until a success occurs. X represents the number of trials before the first success. The probability of x trials before the first success is given by (1-p)^(x-1) * p, where p is the probability of success on a single trial.

    • Probability Density Function (PDF) for Geometric Random Variable: A discrete random variable, X, is geometric if its PDF is:

    • P(X = x) = (1-p)^(x-1) * p, for x = 1, 2, ...

    • 0, otherwise

    • Mean and Variance of Geometric Distribution:

    • Mean (Expected Value): E(X) = 1/p

    • Variance: Var(X) = (1-p)/p²

    Hypergeometric Distribution

    • Key Difference: Sampling without replacement from a finite population. This is in contrast to the binomial distribution, which deals with sampling with replacement.

    • Probability Density Function (PDF) for Hypergeometric Distribution:

    • f(x) = [ (N₁ choose x) * (N - N₁ choose n - x) ] / (N choose n), for x, n—x >= 0 Where:

    • N = Total population size

    • N₁ = Number of items possessing a particular characteristic

    • n = Sample size

    • Constraints: N ≥ N₁, N ≥ n, and n − x ≤ N − N₁ are crucial for the formula to apply.

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    Description

    Test your knowledge on probability distributions, including geometric and hypergeometric distributions. This quiz will cover key concepts such as probability density functions, means, variances, and the differences between sampling with and without replacement.

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