Question 1

Professional sample surveys use careful random samples, usually by randomly dialing telephone numbers, to come close to an SRS. But the results that a sample survey actually obtains may be strongly biased because

Accepted Answer

Many people refuse to respond to telephone surveys, which can result in nonresponse bias. Nonresponse bias occurs when individuals who decline to participate in a survey have different opinions or characteristics than those who do participate, leading to a biased sample. Therefore, even carefully conducted random samples can be biased if a high proportion of invited individuals refuse to participate.

Question 2

In order to gauge student opinion on his grading procedures, the professor divides the class into two groups: undergraduate students and graduate students. He then takes random samples from each group. This is an example of:

Accepted Answer

This is an example of stratified random sampling, as the population (the class) is divided into two strata (undergraduate and graduate students) and then random samples are taken from each stratum. This ensures that both groups are represented in the sample and allows for direct comparison between the opinions of the two groups.

Question 3

You want to know the opinions of American school teachers about establishing a national test for high school graduation. You obtain a list of the members of the National Education Association (the largest teachers' union) and mail a questionnaire to 2500 teachers chosen at random from this list. In all, 1347 teachers return the questionnaire. The sampling frame is

Accepted Answer

The sampling frame is the list or population from which a sample is taken. In this case, it's all members of the National Education Association, as the 2500 teachers were chosen randomly from this list.

Question 4

A survey was sent to a simple random sample of college sophomores. The sample size was 200. When asked whether or not they liked Frank Sinatra's music, 40 of these students did not give any answer. This is an example of

Accepted Answer

The 40 students who did not give any answer represent a nonresponse in the survey, which means they did not participate, or their answer was missing.

Question 5

A pollster wants to ask a sample of undergraduates at State Tech how they feel about a proposal to build a new dorm in the place of the school's largest commuter parking lot. Opinions may differ depending on whether the student is a commuter or resident, so the pollster takes separate SRSs of commuters and resident students and combines them to form his sample. He used a:

Accepted Answer

The pollster used stratified random sampling by dividing the population into two strata - commuters and residents - and taking separate SRSs from each stratum. This ensures that both groups are represented in the sample and that the sample is more representative of the population as a whole.

Question 6

To study the security protocols at a major airport, ten passengers were randomly selected from each flight leaving the airport on a particular day and questioned about the security efforts they experienced while at the airport. This is an example of

Accepted Answer

This is an example of stratified sampling because the population (all passengers leaving the airport on a particular day) is divided into smaller groups (flights) and random samples are taken from each of these groups (ten passengers from each flight).

Question 7

In 2014 Scotland was considering independence from England, going so far as to take a referendum vote. One opinion poll taken at the time showed that 51 percent of Scots favored "independence." In another poll taken at that same time, only 34 percent favored being "separate" from England. The primary reason these results differed by so much is that:

Accepted Answer

The difference in the wording of the questions ("independence" vs. "separate") likely influenced how respondents answered, causing the significant difference in results. This highlights the importance of carefully considering the wording of poll questions to ensure accurate results. Choices A, C, and D are not relevant to explaining the difference in results between the two polls.

Question 8

Which of the following is a source of nonsampling error in a sample survey?

Accepted Answer

The answer of Which of the following is a source...

Question 9

A report from the U.S. Department of Health and Human Services estimated that 10.2 percent of Americans in 2014 had used illicit drugs with a margin of error of ± 0.18 percent. Suppose that many of those asked about their behavior give an answer that isn't the truth because they fear that their answer will go to law enforcement officials.

Accepted Answer

This is a nonsampling error, as it is not related to the methodology of sampling itself but rather to the honesty of the responses given. It causes bias because it skews the results away from the true value and towards an underestimation of the prevalence of illicit drug use.

Question 10

Professor Lilli Gans wishes to study the relationship between a person's zodiac sign and his or her political opinions. She obtains the birthdays of all 816 students enrolled in her Astrology 101 course. Then she uses a random digits table to choose 10 students from each of the twelve zodiac signs. For example, students born from March 21 until April 19 have the Aries zodiac sign, and Professor Gans chooses 10 Aries students at random. She uses a different part of the table of random digits to choose students having each sign. After obtaining her sample, Professor Gans has the selected students fill out a questionnaire.
Professor Gans has obtained a

Accepted Answer

The sampling method used is a stratified random sample, where the strata are students with different zodiac signs. This is because the professor intentionally chooses to sample from each zodiac sign separately, using a different part of the random digits table for each sign. The purpose of the study is to study the relationship between zodiac signs and political opinions, so zodiac sign is the main variable of interest and is used as the basis for stratification.

Question 11

Which of the following sources of error is included in the margin of error?

Accepted Answer

The margin of error accounts for the variability that may arise from random sampling.

Question 12

Some common sources of nonsampling error in samples of human populations are

Accepted Answer

The answer of Some common sources of nonsampling error in...

Question 13

Concerned about the sanitation training practices of its employees, a major fast-food restaurant chain randomly selected 40 of its restaurants nationwide. All employees at these 40 restaurants were tested for their knowledge of both the restaurant chain and local health code practices. This is an example of:

Accepted Answer

This is an example of cluster sampling as the 40 restaurants were randomly selected as clusters and all employees within each selected cluster were tested.

Question 14

A(n) __________ is a list of units from which a sample is chosen.

Accepted Answer

A sampling frame is a list of units from which a sample is chosen. This list can be used to define the population from which the sample is being drawn. Therefore, option C is the correct choice. Option A (individual) refers to a single unit or person, option B (population) refers to the larger group of interest, and option D (treatment) refers to the intervention or variable being studied.

Question 15

An overnight opinion poll calls randomly selected telephone numbers. This polling method misses all people without a phone. Which of the following types of errors is present in this situation?

Accepted Answer

The type of error present in this situation is sampling error. This is because the poll is conducted by randomly selecting telephone numbers, which means that there is a possibility of excluding a certain group of people who do not have a phone. This exclusion can lead to an inaccurate representation of the population, resulting in a sampling error.

Question 16

To obtain student opinions on a particular issue, students were identified by major, and five students were randomly selected from within each major to be interviewed. This is an example of

Accepted Answer

The sampling method described is stratified sampling, as the population (students) was first divided into strata based on their majors, and then a random sample of five students was taken from within each stratum to ensure representation from each major.

Question 17

Increasing the size of a probability sample

Accepted Answer

Increasing the size of a probability sample decreases the variability of a sample statistic. This is because larger sample sizes lead to a more accurate representation of the population, which reduces the impact of random sampling error.

Question 18

Professor Lilli Gans wishes to study the relationship between a person's zodiac sign and his or her political opinions. She obtains the birthdays of all 816 students enrolled in her Astrology 101 course. Then she uses a random digits table to choose 10 students from each of the twelve zodiac signs. For example, students born from March 21 until April 19 have the Aries zodiac sign, and Professor Gans chooses 10 Aries students at random. She uses a different part of the table of random digits to choose students having each sign. After obtaining her sample, Professor Gans has the selected students fill out a questionnaire.
One of the questions in Professor Gans's questionnaire asks whether the student has ever given money to the American Nazi Party. Any students who have done so are likely to lie and say "No," rather than admit the truth. This is an example of

Accepted Answer

This is an example of a nonsampling error, which occurs when errors are made in data collection or analysis. In this case, the error arises from the students' reluctance to admit to giving money to a controversial organization.

Question 19

To obtain faculty opinions on a particular issue, the chief academic officer started with the five schools making up the university. Within each school, she randomly selected two departments. Once the departments were selected, seven faculty members in those departments were selected at random (or all if there were fewer than seven) to be interviewed. This is an example of:

Accepted Answer

This is an example of sampling in stages because the selection process occurs in multiple steps: first selecting schools, then departments within those schools, and finally faculty members within those departments.

Question 20

When a sample survey asks people about their age or some physical characteristic, such as weight, some people who feel self-conscious may not give accurate responses.

Accepted Answer

This is a nonsampling error because it is not related to the method of sampling, but rather the respondents' tendency to provide inaccurate information. It causes bias because it can skew the results if those who are self-conscious are more likely to provide inaccurate responses, leading to an inaccurate representation of the population.

Quiz 4: Sample Surveys in the Real World