500 câu trắc nghiệm Kinh tế lượng – 1A

Identify the type of observational study.

14) A statistical analyst obtains data about ankle injuries by examining a hospital’s records from the
past 3 years.
● Retrospective
○ Cross-sectional
○ Prospective
○ None of these

Identify which of these types of sampling is used: random, stratified, systematic, cluster, convenience.

15) A tax auditor selects every 1000th income tax return that is received.
○ Random
● Systematic
○ Convenience
○ Cluster
E) Stratified

16) A pollster uses a computer to generate 500 random numbers, then interviews the voters corresponding to those numbers.
● Stratified
○ Cluster
○ Convenience
○ Systematic
E) Random

SHORT ANSWER.

Write the word or phrase that best completes each statement or answers the question. Provide an appropriate response.

17) Define random sample. Explain why this is important in design of experiments.

In random sampling, each member of the population has an equal chance of being selected. Random sampling provides us with the best representative sample in which all groups of the population are approximately proportionately represented. Careless sampling can easily result in a biased sample which may be useless

18) Define sampling error and nonsampling error. Give examples of nonsampling error.

Sampling error is the difference between a sample result and the true population result. Such an error results from chance sample fluctuations. A nonsampling error occurs when the sample data are incorrectly collected, recorded, or analyzed. Examples include nonrandom samples, defective measuring instruments, biased survey questions, a large number of refusals, copying sample data incorrectly.

19) A market researcher obtains a sample of 50 people by standing outside a store and asking every 20th person who enters the store to fill out a survey until she has 50 people. What sampling method is being used here? Will the resulting sample be a random sample? Will it be a simple random sample? Explain your thinking.

This is systematic sampling. The sample obtained will be a random sample because everyone has the same chance of being chosen but will not be a simple random sample as different samples of 50 people have different chances of being chosen. Specifically, the sample is random because each person has one chance in twenty of being selected. The sample is not simple random because different samples of size 50 by this design have different chances of being selected due to the numbers of people arriving at the store at different times.

20) Explain the difference between stratified and cluster sampling.

In both cluster sampling and stratified sampling, sub-groups (clusters or strata) are formed. However, in stratified sampling, all strata are used and a sample is selected from each strata. In cluster sampling, a sample of the clusters is first selected, then all members of those clusters are selected.