Reading 10: Sampling and Estimation - LOS a ～ Q6-8 simple, style

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答案和详解如下：

6.A simple random sample is a sample constructed so that:

A)   the sample size is random.

B)   each element of the population has the same probability of being selected as part of the sample.

C)   the sample size is greater than 30.

D)   each element of the population is also an element of the sample.

The correct answer was B)

Simple random sampling is a method of selecting a sample in such a way that each item or person in the population being studied has the same (non-zero) likelihood of being included in the sample.

7.An analyst wants to generate a simple random sample of 500 stocks from all 10,000 stocks traded on the New York Stock Exchange, the American Stock Exchange, and NASDAQ. Which of the following methods is least likely to generate a random sample?

A)   Listing all the stocks traded on all three exchanges in alphabetical order and selecting every 20th stock.

B)   Writing the name of each stock on a piece of paper, putting them in a hat, and drawing out 500 names, one at a time.

C)   Assigning each stock a unique number and generating a number using a random number generator. Then selecting the stock with that number for the sample and repeating until there are 500 stocks in the sample.

D)   Using the 500 stocks in the S& 500.

The correct answer was D)

The S& 500 is not a random sample of all stocks traded in the U.S. because it represents the 500 largest stocks. The other three choices are legitimate methods of selecting a simple random sample.

8.A sample of five numbers drawn from a population is (5, 2, 4, 5, 4). Which of the following statements concerning this sample is TRUE?

A)   The sampling error of the sample is equal to the standard error of the sample.

B)   The mean of the sample is ∑X / (n-1) = 5.

C)   The standard error of the sample mean is: s / (n-1)^1/2 =.75.

D)The variance of the sample is: ∑(x₁ - mean of the sample)² / (n-1) = 1.5.

The correct answer was D)

The mean of the sample is ∑X / n = 20/5 = 4. The standard error of the sample mean is s / n^1/2 =  1.225/2.23 = 0.547. The sampling error of the sample is the difference between a sample statistic and its corresponding population parameter.

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6.A simple random sample is a sample constructed so that:

A)   the sample size is random.

B)   each element of the population has the same probability of being selected as part of the sample.

C)   the sample size is greater than 30.

D)   each element of the population is also an element of the sample.

7.An analyst wants to generate a simple random sample of 500 stocks from all 10,000 stocks traded on the New York Stock Exchange, the American Stock Exchange, and NASDAQ. Which of the following methods is least likely to generate a random sample?

A)   Listing all the stocks traded on all three exchanges in alphabetical order and selecting every 20th stock.

B)   Writing the name of each stock on a piece of paper, putting them in a hat, and drawing out 500 names, one at a time.

C)   Assigning each stock a unique number and generating a number using a random number generator. Then selecting the stock with that number for the sample and repeating until there are 500 stocks in the sample.

D)   Using the 500 stocks in the S& 500.

8.A sample of five numbers drawn from a population is (5, 2, 4, 5, 4). Which of the following statements concerning this sample is TRUE?

A)   The sampling error of the sample is equal to the standard error of the sample.

B)   The mean of the sample is ∑X / (n-1) = 5.

C)   The standard error of the sample mean is: s / (n-1)^1/2 =.75.

D)The variance of the sample is: ∑(x₁ - mean of the sample)² / (n-1) = 1.5.

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