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Solutions to homework problems for isye 6739, a course offered during the summer 2009 semester. The problems cover various topics in statistics and probability, including constructing histograms, minimizing quadratic functions, normal distributions, chi-square, t-distributions, f-distributions, mean squared error, maximum likelihood estimation, and confidence intervals.
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Homework #7 (Covers Modules 27–33) — Due Tuesday 7/7/
All of the following problems are from Hines, et al.
8–1. Elementary data analysis. The shelf life of a high-speed photographic film is being investigated by the manufacturer. The following data are available (in days).
Construct a histogram and comment on the properties of the data.
8–25. Interesting algebra question. Consider the quantity
∑n i=1(xi^ −^ a)
(^2). For what value
of a is this quantity minimized?
9–5. Normal distribution. A population of power supplies for a personal computer has an output voltage that is normally distributed with a mean of 5.00 V and a standard deviation of 0.10 V. A random sample of eight power supplies is selected. Specify the sampling distribution of X¯.
9–23(a). χ^2 quantile. Find χ^20. 95 , 8.
9–24(a). t quantile. Find t 0. 25 , 10.
9–25(a). F quantile. Find F 0. 25 , 4 , 9.
10–1. MSE. Suppose we have a random sample of size 2n from a population denoted X, and E[X] = μ and Var(X) = σ^2. Let
2 n
∑^2 n
i=
Xi and X¯ 2 =
n
∑^ n
i=
Xi
be two estimators of μ. Which is the better estimator of μ? Explain your choice.
10–13. Geometric MLE. Let X be a geometric random variable with parameter p. Find the maximum likelihood estimator of p, based on a sample of size n.
10–41(a). Confidence interval (known variance). A civil engineer is analyzing the compressive strength of concrete. Compressive strength is approximately normally dis- tributed with a variance of σ^2 = 1000 (psi)^2. A random sample of 12 specimens has a mean compressive strength of ¯x = 3250 psi. Construct a 95% two-sided confidence interval on mean compressive strength.