Q1. An equity analyst needs to select a representative sample of manufacturing stocks. Starting with the population of all publicly traded manufacturing stocks, she classifies each stock into one of the 20 industry groups that form the Index of Industrial Production for the manufacturing industry. She then selects a number of stocks from each industry based on its weight in the index. The sampling method the analyst is using is best characterized as:

A)   data mining.

B)   nonrandom sampling.

C)   stratified random sampling.

Q2. An analyst divides the population of U.S. stocks into 10 equally sized sub-samples based on market value of equity. Then he takes a random sample of 50 from each of the 10 sub-samples and pools the data to create a sample of 500. This is an example of:

A)    simple random sampling.

B)    stratified random sampling.

C)    systematic cross-sectional sampling.

Q3. Which of the following is least likely a step in stratified random sampling?

A)     The population is divided into strata based on some classification scheme.

B)     The size of each sub-sample is selected to be the same across strata.

C)     The sub-samples are pooled to create the complete sample.

Q4. Thomas Merton, a car industry analyst, wants to investigate a relationship between the types of ads used in advertising campaigns and sales to customers in certain age groups. In order to make sure he includes manufacturers of all sizes, Merton divides the industry into four size groups and draws random samples from each group. What sampling method is Merton using?

A)   Cross-sectional sampling.

B)   Stratified random sampling.

C)   Simple random sampling.

答案和详解如下：

Q1. An equity analyst needs to select a representative sample of manufacturing stocks. Starting with the population of all publicly traded manufacturing stocks, she classifies each stock into one of the 20 industry groups that form the Index of Industrial Production for the manufacturing industry. She then selects a number of stocks from each industry based on its weight in the index. The sampling method the analyst is using is best characterized as:

A)   data mining.

B)   nonrandom sampling.

C)   stratified random sampling.

Correct answer is C)

In stratified random sampling, a researcher classifies a population into smaller groups based on one or more characteristics, takes a simple random sample from each subgroup based on the size of the subgroup, and pools the results.

Q2. An analyst divides the population of U.S. stocks into 10 equally sized sub-samples based on market value of equity. Then he takes a random sample of 50 from each of the 10 sub-samples and pools the data to create a sample of 500. This is an example of:

A)    simple random sampling.

B)    stratified random sampling.

C)    systematic cross-sectional sampling.

Correct answer is B)

In stratified random sampling we first divide the population into subgroups, called strata, based on some classification scheme. Then we randomly select a sample from each stratum and pool the results. The size of the samples from each strata is based on the relative size of the strata relative to the population. 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.

Q3. Which of the following is least likely a step in stratified random sampling?

A)     The population is divided into strata based on some classification scheme.

B)     The size of each sub-sample is selected to be the same across strata.

C)     The sub-samples are pooled to create the complete sample.

Correct answer is B)

In stratified random sampling we first divide the population into subgroups, called strata, based on some classification scheme. Then we randomly select a sample from each stratum and pool the results. The size of the samples from each strata is based on the relative size of the strata relative to the population and are not necessarily the same across strata.

Q4. Thomas Merton, a car industry analyst, wants to investigate a relationship between the types of ads used in advertising campaigns and sales to customers in certain age groups. In order to make sure he includes manufacturers of all sizes, Merton divides the industry into four size groups and draws random samples from each group. What sampling method is Merton using?

A)   Cross-sectional sampling.

B)   Stratified random sampling.

C)   Simple random sampling.

Correct answer is B)

In stratified random sampling, we first divide the population into subgroups based on some relevant characteristic(s) and then make random draws from each group.

bbca

Q2. Joe Sutton is evaluating the effects of the 1987 market decline on the volume of trading. Specifically, he wants to test whether the decline affected trading volume. He selected a sample of 500 companies and collected data on the total annual volume for one year prior to the decline and for one year following the decline. What is the set of hypotheses that Sutton is testing?

A)   H₀: μ_d = μ_d0 versus H_a: μ_d ≠ μ_d0.

B)   H₀: μ_d ≠ μ_d0 versus H_a: μ_d = μ_d0.

C)   H₀: μ_d = μ_d0 versus H_a: μ_d > μ_d0.

Correct answer is A)

This is a paired comparison because the sample cases are not independent (i.e., there is a before and an after for each stock). Note that the test is two-tailed, t-test.

Q3. An analyst wants to determine whether the monthly returns on two stocks over the last year were the same or not. What test should she use if she is willing to assume that the returns are normally distributed?

A)   A difference in means test only if the variances of monthly returns are equal for the two stocks.

B)   A paired comparisons test because the samples are not independent.

C)   A difference in means test with pooled variances from the two samples.

Correct answer is B)

A paired comparisons test must be used. The difference in means test requires that the samples be independent. Portfolio theory teaches us that returns on two stocks over the same time period are unlikely to be independent since both have some systematic risk.

Q4. An analyst for the entertainment industry theorizes that betas for most firms in the industry are higher after September 11, 2001. She sampled 31 firms comparing their betas for the one-year period before and after this date. Based on this sample, she found that the mean differences in betas were 0.19, with a sample standard deviation of 0.11. Her null hypothesis is that the betas are the same before and after September 11. Based on the results of her sample, can we reject the null hypothesis at a 5% significance level and why? Null is:

A)   not rejected. The critical value exceeds the t-value by 7.58.

B)   rejected. The t-value exceeds the critical value by 5.67.

C)   rejected. The t-value exceeds the critical value by 7.58.

Correct answer is C)         

The t-statistic for paired differences:

t = (d – u_{d 0}) / s_d and s_d = s_d / √n

t = 9.62 from a table with 30 df, the critical value = 2.042

thx a lot!

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