Research Methods Chapter 7: Sampling

systematic sampling

A probability sampling technique in which the researcher counts off members of a population to achieve a sample, using a randomly chosen interval (e.g., every nth person, where n is a randomly selected number).

Multistage sampling

A probability sampling technique involving at least two stages: a random sample of clusters followed by a random sample of people within the selected clusters.

Representative sample

A sample in which all members of the population of interest are equally likely to be included (usually through some random method), and therefore the results can generalize to the population of interest. Also called unbiased sample.

Biased Sample

A sample in which some members of the population of interest are systematically left out, and as a consequence, the results from the sample cannot generalize to the population of interest. Also called unrepresentative sample.

Census

A set of observations that contains all members of the population of interest.

Snowball sampling

A variation on purposive sampling, a biased sampling technique in which participants are asked to recommend acquaintances for the study.

What kind of sample is best for external validity? a sample where each member of the population has an equal chance of being selected a sample that can be collected as quickly as possible a sample that includes the majority of the population the largest sample possible

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A ________ is the entire set of people in which the researchers are interested. Correct! population representative sample quota sample biased sample

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A college administrator knows that 70 percent of the students at his college are from out of state, so he decides to make sure that he includes 70 out-of-state students and 30 in-state students in his survey about admission practices at the college. He has a list of all of the out-of-state and all of the in-state students currently enrolled at the college. He randomly selects 70 students from the out-of-state list and 30 students from the in-state list. What sampling method is he using? Correct! stratified random sampling multi-stage sampling quota sampling cluster sampling

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Mr. Stratford is the president of a national organization of lesbian, bisexual, gay, and transgender people in the United States. He wants to survey 1,000 members of his organization about the position they want the organization to take on several political issues. He knows that transgender people make up only 5 percent of his organization, but he wants to make sure that their views are accurately represented. He decides that he will randomly sample 100 transgender members and then adjust the final results so that transgender people are weighted to their actual proportion in the organization. Is Mr. Stratford collecting a representative sample? Correct! Yes, because the transgender people in the final sample were sampled randomly from the population of transgender people in the organization. No, because straight people are not included in the sample. Yes, because 1,000 people is enough to make a representative sample. No, because the transgender people are over-represented in the final sample.

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The superintendent of schools in a small town in Ohio made a lot of policy changes to the way school administration worked in his district. A researcher at a nearby university wanted to look at what teachers in his district thought about the changes. The researcher made a list of all of the schools in the district and used a random number generator to select a sample of five schools from the district. Then the researcher interviewed every teacher at each of those five schools. What sampling method did the researcher use? Correct! cluster sampling purposive sampling systematic sampling simple random sampling

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Which sample would be most likely to represent the population of American teenagers? Correct! a cluster sampling of 1,000 teenagers from around the United States a purposive sample of 1,250 U.S. teenagers a convenience sample of 1,200 U.S. teenagers a snowball sampling of 1,500 teenagers from around the United States

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________ is when you study every member of a population. Correct! A census A biased sample A representative sample Oversampling

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Externally valid samples are more important for some research questions than for others. For which of the following research questions will it be most important to use an externally valid sampling technique? 1. estimating the proportion of U.S teens who are depressed 2. testing the association between depression and illegal drug use in U.S teens 3. testing the effectiveness of support groups for teens with depression

1. Estimating the proportion of U.S teens who are depressed

A sample is always __________ a population. larger than Correct! smaller than the same size as unrelated to

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Dr. Lawrence is the director of Counseling Services at her university. She is planning to conduct a survey of 100 students at the university to see how aware they are of the counseling services that are offered at the university. She wants the proportion of males and females in her sample to reflect the proportion in the university as a whole (55 percent female and 45 percent male). Dr. Lawrence plans to stand in the Student Union and ask people to participate until she has given the survey to 55 females and 45 males. Is Dr. Lawrence collecting a representative sample? No, because 100 people is not enough for a representative sample. Correct! No, because the participants are selected nonrandomly. Yes, because the sample includes a representative proportion of males and females. Yes, because all of the students in her sample attend her university.

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Dr. Rhodes is interested in how differing levels of light affect how people perceive color. He finds participants for this research study by making an announcement in several psychology classes at his university. What kind of sampling method is Dr. Rhodes using? systematic sampling Correct! convenience sampling snowball sampling cluster sampling

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What sample size is often cited as the optimal balance between accuracy and effort? 1. 2,000 2. 1,000 3. 500 4. 100

2. 1,000

Mr. Stratford is the president of a national organization of lesbian, bisexual, gay, and transgender people in the United States. He wants to survey 1,000 members of his organization about the position they want the organization to take on several political issues. He knows that transgender people make up only 5 percent of his organization, but he wants to make sure that their views are accurately represented. He decides that he will randomly sample 100 transgender members and then adjust the final results so that transgender people are weighted to their actual proportion in the organization. Is Mr. Stratford collecting a representative sample? 1. No, because straight people are not included in the sample. 2. Yes, because the transgender people in the final sample were sampled randomly from the population of transgender people in the organization. 3. No, because the transgender people are over-represented in the final sample. 4. Yes, because 1,000 people is enough to make a representative sample.

2. Yes, because the transgender people in the final sample were sampled randomly from the population of transgender people in the organization.

A political research center obtains a list of phone numbers for all registered voters in Texas and uses a random number generator to select 1,000 of the phone numbers to call. They ask each voter which gubernatorial candidate they plan to vote for in the upcoming election. What is the population of interest that the research center wants to generalize to? all of the people likely to vote for the Republican candidate for governor all Americans Correct! all registered voters in Texas all Texans

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Dr. Rhodes is interested in how differing levels of light affect how people perceive color. He finds participants for this research study by making an announcement in several psychology classes at his university. Should Dr. Rhodes be concerned about using this sampling method? No, because his sample is representative of college students. You Answered Yes, because his sample will not be representative of people in general. Correct Answer No, because external validity probably doesn't matter for the type of claim he is making. Yes, because extern

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Mr. Stratford is the president of a national organization of lesbian, bisexual, gay, and transgender people in the United States. He wants to survey 1,000 members of his organization about the position they want the organization to take on several political issues. He knows that transgender people make up only 5 percent of his organization, but he wants to make sure that their views are accurately represented. He decides that he will randomly sample 100 transgender members and then adjust the final results so that transgender people are weighted to their actual proportion in the organization. What type of sampling is Mr. Stratford using? You Answered quota sampling cluster sampling Correct Answer oversampling snowball sampling

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The campus safety committee has asked Professor Ibrahim to study bicycling on his campus. He trains two observers and has them observe the number of cyclists and their safety at various points around campus. He selects ten observation locations at random from the places bicycles can be ridden on campus and five one-hour spans of time at random from the daylight hours for each place. He has his observers make observations at each of the ten places for each of the five time spans. What type of sampling is he using? simple random sampling You Answered systematic sampling Correct Answer multistage sampling stratified random sampling

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The student government at a college is interested in determining how important intercollegiate sports are to the students there. Since all students have e-mail accounts, they are able to send a survey to all the students. About 50 percent of the students respond. Which is the most likely bias in this sample? random sampling bias You Answered a bias from contacting only those the student government could easily contact Correct Answer self-selection bias convenience sampling bias

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Typically, in which type of claim is it most important to have a random sample? association anecdotal Correct! frequency causal

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Which of the following is considered a biased sampling method? cluster sampling simple random sampling Correct! convenience sampling stratified random sampling

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Which of the following is considered a representative sampling method? convenience sampling snowball sampling Correct! systematic sampling self-selected sampling

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________ is when you study every member of a population. A biased sample A representative sample A census Oversampling

3. A Census

A researcher's population of interest is New York City's dog owners. Which of the following samples is most likely to generalize to this population interest? 1. A sample of 25 dogs owners visiting dog friendly NY city parks 2. A sample of 25 dog owners who have appointments for their dogs at the veterinarians in the NYC area. 3. A sample of 25 dog owners selected at random from NYC pet registration records 4. A sample of 25 dog owners who regularly log into the nycdog.org website

3. A sample of 25 dog owners selected at random from the NYC pet registration records

Which of the following samples is most likely to generalize to its population of interest? 1. a convenience sample of 12,000 2. a quota sample of 120 3. a cluster sample of 120 4. a self-selected sample of 120,000

3. Cluster sampling

A political research center obtains a list of phone numbers for all registered voters in Texas and uses a random number generator to select 1,000 of the phone numbers to call. They ask each voter which gubernatorial candidate they plan to vote for in the upcoming election. What sampling method is being used? stratified random sampling multistage sampling systematic sampling Correct! simple random sampling

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Beth is working on a research study focused on attention span in children. Among the participants, the group of 11-year-old boys is underrepresented. Beth asks her 11-year-old brother to distribute flyers about participation in the study to his male classmates and soccer team. What type of sampling is this? self-selected multistage random Correct! snowball

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Dr. Jennings is doing a study on the experience of being a racial minority on a college campus. He goes to the Asian Student Association, Black Student Union, and Hispanic Student Group on his campus to recruit participants for his study. Dr. Jennings only includes Asians, African-Americans, and Hispanic participants in his study. What type of sampling is Dr. Jennings using? quota sampling systematic sampling cluster sampling Correct! purposive sampling

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Population

A larger group from which a sample is drawn; the group to which a study's conclusions are intended to be applied. Also called population of interest.

Cluster sampling

A probability sampling technique in which clusters of participants within the population of interest are selected at random, followed by data collection from all individuals in each cluster.

Dr. Lawrence is the director of Counseling Services at her university. She is planning to conduct a survey of 100 students at the university to see how aware they are of the counseling services that are offered at the university. She wants the proportion of males and females in her sample to reflect the proportion in the university as a whole (55 percent female and 45 percent male). Dr. Lawrence plans to stand in the Student Union and ask people to participate until she has given the survey to 55 females and 45 males. What type of sampling method is Dr. Lawrence going to use? stratified random sampling multi-stage sampling cluster sampling Correct! quota sampling

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The directors of an annual community concert want to find the musical preferences of the audience. The ushers place a survey card on every sixth seat beginning with the second seat (2 and 6 were chosen from a random number table). All of the cards are returned as the audience leaves. Which type of sampling is being used? cluster sampling stratified random sampling multistage sampling Correct! systematic sampling

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What sample size is often cited as the optimal balance between accuracy and effort? 2,000 500 100 Correct! 1,000

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Which of the following is most important for enhancing external validity? a large sample size random assignment using measures that are valid and reliable Correct! random sampling

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Which of the following four terms does not belong? 1. Generalization sample 2. externally valid sample 3. Representative sample 4. biased sample

4. Biased Sample

The superintendent of schools in a small town in Ohio made a lot of policy changes to the way school administration worked in his district. A researcher at a nearby university wanted to look at what teachers in his district thought about the changes. The researcher made a list of all of the schools in the district and used a random number generator to select a sample of five schools from the district. Then the researcher interviewed every teacher at each of those five schools. What sampling method did the researcher use? 1. systematic sampling 2.simple random sampling 3. purposive sampling 4. cluster sampling

4. Cluster Sampling

Mr. Stratford is the president of a national organization of lesbian, bisexual, gay, and transgender people in the United States. He wants to survey 1,000 members of his organization about the position they want the organization to take on several political issues. He knows that transgender people make up only 5 percent of his organization, but he wants to make sure that their views are accurately represented. He decides that he will randomly sample 100 transgender members and then adjust the final results so that transgender people are weighted to their actual proportion in the organization. What type of sampling is Mr. Stratford using? 1. snowball sampling 2. cluster sampling 3. quota sampling 4. oversampling

4. Oversampling

Quota sampling

A biased sampling technique in which a researcher identifies subsets of the population of interest, sets a target number for each category in the sample, and nonrandomly selects individuals within each category until the quotas are filled.

Purposive sampling

A biased sampling technique in which only certain kinds of people are included in a sample.

stratified random sampling

A form of probability sampling; a random sampling technique in which the researcher identifies particular demographic categories of interest and then randomly selects individuals within each category.

oversampling

A form of probability sampling; a variation of stratified random sampling in which the researcher intentionally overrepresents one or more groups.

Self Selection

A form of sampling bias that occurs when a sample contains only people who volunteer to participate.

convenience sampling

Choosing a sample based on those who are easiest to access and readily available; a biased sampling technique.

What are the four ways of selecting biased sample of a population of interest? which subsets are more likely to be selected in each case?

Convenience: Samples are chosen from an area that is most convenient for researchers Purposive: Studying only one kind of people Snowball: starting off with two participants and having them recruiter their own acquaintances of their choosing which causes bias Quota: wanting equal of each population

Why are convenience, purposive, snowball, and quota sampling NOT examples of representative sampling?

Convenience: You're not creating a random sample Purposive: You're not creating a random sample Snowball: Because you are having your participants choose who they might be more biased too in their sampling Quota: not an accurate representation of how big or small populations are with the whole population

In your own words, describe the difference between random sampling and random assignment?

Random Sampling: Is when you are creating a sample group using some random method. Using external validity. Random Assignment: Is used only in experimental designs. sample group is already made and typically are now divided into different groups that have an experimental and control group. Internal validity.

What are the five techniques for selecting a representative sample of a population of interest? Where does the randomness enter into each of these five selection processes?

Simple random sampling: Using programs or techniques that generate numbers that are random. Hat names technique Cluster Sampling/Multistage sampling: Iowa schools-choosing five at random and then using all the students from those five schools. Stratified random sampling: Sampling 1,000 Canadians and wanting to included south asian Canadians. They would randomly choose 40 south asian Canadians and then the rest Canadians to equal the percentage (4%) of asian Canadians in Canada. Oversampling: Instead of choosing 4% (40) of South Asian Americans, the researcher would 1,000 which is oversampling systematic sampling: Counting off in class while students are lined up randomly

sample

The group of people, animals, or cases used in a study; a subset of the population of interest.

Simple random sampling

The most basic form of probability sampling, in which the sample is chosen completely at random from the population of interest (e.g., drawing names out of a hat).

Probability Sampling

The process of drawing a sample from a population of interest in such a way that each member of the population has an equal chance of being included in the sample, usually via random selection. Also called random sampling

Random Assignment

The use of a random method (e.g., flipping a coin) to assign participants into different experimental groups.