##### General Statistics: Ch 1, Sec 1.4 HW

College: First year, College: Second year, College: Third year, College: Fourth year

What is the difference between a random sample and a simple random sample?

With a random sample, each individual has the same chance of being selected.

With a simple random sample, all samples of the same size have the same chance of being selected.

Determine whether the description corresponds to an observational study or an experiment.

Research is conducted to determine if there is a relation between stomach cancer and alcohol consumption.

Observational study

Determine whether the given description corresponds to an observational study or an experiment.

In a study of 357 boys with a particular disease, the subjects were given certain drugs to determine if the drugs have an effect on the disease.

The given description corresponds to an experiment.

Determine whether the description below corresponds to an observational study or an experiment.

In a study sponsored by a company, 13,125 people were asked what contributes most to their anxiety, and 47% of the respondents said that it was their health.

The study is an observational study because the survey subjects were not given any treatment.

Identify the type of sampling used (random, systematic, convenience, stratified, or cluster sampling) in the situation described below.

A man is selected by a marketing company to participate in a paid focus group. The company says that the man was selected because everyone in six randomly selected towns was being selected.

Cluster sampling

Identify the type of sampling used (random, systematic, convenience, stratified, or cluster sampling) in the situation described below.

In a poll conducted by a certain research center, 920 adults were called after their telephone numbers were randomly generated by a computer, and 68% were able to correctly identify the attorney general.

Random sampling

Identify which type of sampling is used: random, systematic, convenience, stratified, or cluster.

A magazine asks its readers to call in their opinion regarding the quality of the articles.

Convenience

Identify the type of sampling used: random, systematic, convenience, stratified, or cluster.

To estimate the percentage of defects in a recent manufacturing batch, a quality control manager at Ford selects every 14th truck that comes off the assembly line starting with the ninth until she obtains a sample of 60 trucks.

Systematic

Identify the type of sampling used (random, systematic, convenience, stratified, or cluster sampling) in the situation described below.

A man experienced a tax audit. The tax department claimed that the man was audited because he was randomly selected from all men in his age group.

Stratified sampling

Identify which type of sampling is used: random, systematic, convenience, stratified, or cluster.

To determine customer opinion of their safety features, Daimler – Chrysler randomly selects 50 service centers during a certain week and surveys all customers visiting the service centers.

Cluster

A researcher selects every 648th social security number and surveys the corresponding person.

Systematic sampling

Determine whether the sample described below is a simple random sample.

A quality control engineer selects every 5000th chocolate that is produced.

The sample is not a simple random sample because every sample of the same size does not have the same chance of being selected.

Determine whether the sample described below is a simple random sample.

In order to test for a difference in the way that workers and non-workers purchase magazines, a research institution polls exactly 522 adult workers and 522 adult non-workers randomly selected from adults in the United States.

The sample is not a simple random sample because every sample of size 1308 does not have the same chance of being selected.

Determine whether the sample described below is a simple random sample.

In the last election, 183,644 adults voted in a county. A researcher plans to conduct a survey of 800 of those voters. After obtaining a list of those who voted, he numbers the list from 1 to 183,644, and then he uses a computer to randomly generate 800 numbers between 1 and 183,644. His sample consists of the voters corresponding to the selected numbers.

The sample is a simple random sample because every sample of size 800 has the same chance of being selected.

Determine whether the sample described below is a simple random sample.

According to a realtors association, names of potential house buyers are selected from a variety of different sources. Names from the list are randomly selected in a way that is equivalent to writing the names on slips of paper, mixing them in a bowl, and selecting the required number of potential house buyers.

The sample is a simple random sample because every sample of the same size has the same chance of being selected.

A packager wraps one item every 20 minutes, so 120 items are completed in his first week of work. His manager checks his work by randomly selecting a day of the week, then reviewing all the items he completed that day.

Does this sampling plan result in a random sample?

Does this sampling plan result in a simple random sample?

Yes, because each item has an equal chance of being selected.

No, because all possible groups of n items do not have an equal chance of being selected.

Identify the type of observational study.

A researcher plans to obtain data by examining the financial transactions of victims who perished in a bombing.

retrospective

Identify the type of observational study (cross-sectional, retrospective, or prospective) described below.

A research company uses a device to record the viewing habits of about 15,000 households, and the data collected over the past 10 years will be used to determine whether the proportion of households tuned to a particular educational program increased.

A retrospective study

Which sampling method divides the population up into sections, randomly selects some of those sections, then chooses all the members from the selected sections to study?

**Cluster** sampling involves subdividing the population
and using all members from a randomly selected group of subdivisions

Which sampling method subdivides the population into categories sharing similar characteristics and then selects a sample from each subdivision?

**Stratified** sampling method involves subdividing the
population and uses a sample of members from each subdivision of the population.

A study is conducted to measure children's growth rates without any treatment applied to the children. What best classifies this study?

An **observational study** involves observing and
measuring specific characteristics without attempting to modify the
subjects being studied.

Which of the following corresponds to the case when every sample of size n has the same chance of being chosen?

A **simple random sample** of n subjects is selected in
such a way that every possible sample of the same size n has the same
chance of being chosen