Exam 5: Sampling Distributions

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A point estimator of a population parameter is a rule or formula which tells us how to use sample data to calculate a single number that can be used as an estimate of the population parameter.

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Suppose students' ages follow a skewed right distribution with a mean of 23 years old and a standard deviation of 4 years. If we randomly sample 200 students, which of the following Statements about the sampling distribution of the sample mean age is incorrect?

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Which of the following statements about the sampling distribution of the sample mean is incorrect?

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Suppose a random sample of n=36n = 36 measurements is selected from a population with mean μ=256\mu = 256 and variance σ2=144\sigma ^ { 2 } = 144 . Find the mean and standard deviation of the sampling distribution of the sample mean xˉ\bar { x } .

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The sample mean, xˉ\bar{x} , is a statistic.

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If xˉ\bar{x} is a good estimator for µ, then we expect the values of x to cluster around µ.

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As the sample size gets larger, the standard error of the sampling distribution of the sample mean gets larger as well.

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Consider the population described by the probability distribution below. x 3 5 7 p(x) .1 .7 .2 a. Find μ\mu . b. Find the sampling distribution of the sample median for a random sample of n=2n = 2 observations from this population. c. Show that the median is an unbiased estimator of μ\mu .

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The probability of success, p, in a binomial experiment is a parameter, while the mean and standard deviation, µ and ?, are statistics.

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The length of time a traffic signal stays green (nicknamed the "green time") at a particular intersection follows a normal probability distribution with a mean of 200 seconds and the standard Deviation of 10 seconds. Use this information to answer the following questions. Which of the Following describes the derivation of the sampling distribution of the sample mean?

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Consider the probability distribution shown here. x 0 2 4 p(x) Let xˉ\bar { x } be the sample mean for random samples of n=2n = 2 measurements from this distribution. Find E(x)E ( x ) and E(xˉ)E ( \bar { x } ) .

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The standard error of the sampling distribution of the sample mean is equal to ?, the standard deviation of the population.

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The Central Limit Theorem states that the sampling distribution of the sample mean is approximately normal under certain conditions. Which of the following is a necessary condition for the Central Limit Theorem to be used?

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A random sample of n=600n = 600 measurements is drawn from a binomial population with probability of success .08.08 . Give the mean and the standard deviation of the sampling distribution of the sample proportion, p^\hat { p } .

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The probability distribution shown below describes a population of measurements that can assume values of 5, 9, 13, and 17, each of which occurs with the same frequency: x 5 9 13 17 p(x) Find E(x)=μE ( x ) = \mu . Then consider taking samples of n=2n = 2 measurements and calculating xˉ\bar { x } for each sample. Find the expected value, E(xˉ)E ( \bar { x } ) , of xˉ\bar { x } .

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Consider the population described by the probability distribution below. x 3 5 7 p(x) .1 .7 .2 a. Find σ2\sigma ^ { 2 } . b. Find the sampling distribution of the sample variance s2s ^ { 2 } for a random sample of n=2n = 2 measurements from the distribution. c. Show that s2s ^ { 2 } is an unbiased estimator of σ2\sigma ^ { 2 } .

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A random sample of n=300\mathrm { n } = 300 measurements is drawn from a binomial population with probability of success .26. Give the mean and the standard deviation of the sampling distribution of the sample proportion, p^\hat { p } .

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The ideal estimator has the greatest variance among all unbiased estimators.

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The Central Limit Theorem guarantees that the population is normal whenever n is sufficiently large.

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The weight of corn chips dispensed into a 14-ounce bag by the dispensing machine has been identified as possessing a normal distribution with a mean of 14.5 ounces and a standard deviation of 0.2 ounce. Suppose 100 bags of chips are randomly selected. Find the probability that the mean weight of these 100 bags exceeds 14.6 ounces.

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