Stats Library

Statistics Assignment Library

  1. Solved: A survey of 120 female freshman showed that 18 did not wish to work after marriage. Find the 95% confidence interval
    A survey of 120 female freshman showed that 18 did not wish to work after marriage. Find the 95% confidence interval of the true proportion of females who do not wish to work after marriage. Solution Let $X$ denote the...
  2. Solved (Free): Let $Y_1, Y2, \cdots, Y_n$ be independent random variables such that each $Y_i$ has a gamma distribution with parameters
    Let $Y_1, Y2, \cdots, Y_n$ be independent random variables such that each $Y_i$ has a gamma distribution with parameters $\alpha_i$ and $\beta$. That is, the distributions of the $Y$'s might have different $\alpha$'s, but all have the same value for...
  3. Solved: The time between release from prison and the commission of another crime is uniformly distributed between 0 and 5 years for a high-risk group
    The time between release from prison and the commission of another crime is uniformly distributed between 0 and 5 years for a high-risk group. Give the equation and graph the pdf for X, the time between release and the commission...
  4. Solved: The article “Modeling Sediment and Water Column Interactions for Hydrophobic Pollutants”
    The article "Modeling Sediment and Water Column Interactions for Hydrophobic Pollutants" (Water Research [1984]: 1169-1174) suggests the uniform distribution on the interval from 7.5 to 20 as a model for x = depth (in centimeters) of the bioturbation layer in...
  5. Solved: The hardness of a piece of ceramic is proportional to the firing time. Assume that a rating system has been devised to rate the hardness of a ceramic piece
    The hardness of a piece of ceramic is proportional to the firing time. Assume that a rating system has been devised to rate the hardness of a ceramic piece and that this measure of hardness is a random variable that...
  6. Solved: Suppose that a class in elementary statistics was allocated 15 minutes to complete a quiz. It can be assumed that the time X it takes to complete
    Suppose that a class in elementary statistics was allocated 15 minutes to complete a quiz. It can be assumed that the time X it takes to complete the quiz is uniformly distributed over the interval [0, 15]. Suppose a student...
  7. Solved (Free): The following data represents viscosity measurements from a batch chemical process. The data is assumed to be normally distributed
    The following data represents viscosity measurements from a batch chemical process. The data is assumed to be normally distributed. The batches are checked for conformance to specification. Batches whose viscosity lies between 84 and 96 are acceptable. A random sample...
  8. Solved:The lifetime $X$ of a device is an exponential random variable with mean = $1/R$
    The lifetime $X$ of a device is an exponential random variable with mean = $1/R$. Suppose that due to irregularities in the production process, the parameter $R$ is random and has a gamma distribution. (a) Find the joint pdf of...
  9. Solved: The useful life of an electrical component is exponentially distributed with a mean of 2,500 hours
    The useful life of an electrical component is exponentially distributed with a mean of 2,500 hours. a. What is the probability the circuit will last more than 3,000 hours? b. What is the probability the circuit will last between 2,500...
  10. Solved (Free): A course has two quizzes of equal weight, a midterm examination that has twice the weight of a quiz
    A course has two quizzes of equal weight, a midterm examination that has twice the weight of a quiz, and a final examination that has twice the weight of the midterm exam. If a student obtains 54% and 60% on...
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