Definitions
A subset of a population used for research
What is a Sample?
A market researcher surveys 85 people on their coffee-drinking habits. She wants to know whether people in the local region are willing to switch their regular drink to something new. The sample is...
What is "the 85 people surveyed"?
The sampling method in which the people who respond to the survey question choose themselves.
What is Voluntary Response Sampling?
The head chef of a restaurant wants to know if he should add more vegetarian options to his menu. To find out the demand for vegetarian dishes amongst his customers, he sends out an email to everyone on the mailing list of the restaurant asking them to fill out a survey.
What is Voluntary Response Sampling?
Your math teacher asks for volunteers to clean up trash. She observes the people to volunteer enjoy picking up trash. She concludes everyone in her class enjoys picking up trash. The type of bias is...
What is Voluntary Response Bias.
All members of a group that you are looking to make generalizations about.
What is a Population?
The state Department of Transportation wants to know about out-of-state vehicles that pass over a toll bridge with several lanes. A camera installed over one lane of the bridge photographs the license plate of every tenth vehicle that passes through that lane. The population is...
What is "all of the vehicles that pass through"?
The sampling method in which the sample is chosen randomly from the population.
What is Simple Random Sampling?
An elementary school principal wants to know more about the prevalence of learning disabilities at her school. She randomly selects 2 grades and has all the children in those grades tested by an educational psychologist.
What is Cluster Sampling?
I ask my students "What do you think of this incredibly fun jeopardy game?"
What is question wording bias .
A selection process in which every item has an equal probability of being chosen.
What is random?
A factory overseer selects 40 threaded rods at random from those produced that week at the factory, then she tests their tensile strength. The sample is...
What is "the 40 threaded rods selected"?
The sampling method in which the population is divided into areas and entire areas (example neighborhoods) are chosen to be part of the sample.
What is Cluster Sampling?
A university wants to find out how far the average student lives from the campus. To investigate this matter, a random number generator is used to select a sample of 250 students from the student registry.
What is Simple Random Sampling?
Your coach wants to know who would like to stay after school to run extra laps so they can record the times down. Only one person ends up staying after school, and they are the slowest on the team. The coach concludes the team is slow and needs extra practice with sprints. The type of bias AND direction are...
What is Nonresponse Bias
A sample where you first divide your population into subgroups, then randomly pick people from each subgroup.
What is a stratified sample?
The owners of a sports stadium wanted to predict what additional refreshment options would sell well. They selected 8000 seat numbers at random and surveyed the occupants of those seats. The population is...
What is "the occupants of all seats in the stadium"?
The sampling method where the researcher picks whoever they see first.
What is non random/judgment Sampling?
A Ph.D. student is looking for research participants for her dissertation. She decides to recruit the first 10 students she sees.
What is judgement (non random) Sampling?
A custodian asked, "Raise your hand if you've been messy and left food all over the lunchroom which is very inconsiderate." No students raise their hand, so they custodian concludes the lunchroom is perfectly clean and all students pick up after themselves. The type of bias and direction are...
What is Wording of the Question and underestimation.
A sample that is NOT representative of the population it was drawn from.
What is a Biased Sample?
A city council member wanted to know how her constituents felt about a planned rezoning. She randomly selected 700,575 names from the city phone directory and conducted a phone survey. The sample is...
What is "the 700,575 people selected"?
A sample where a rule is used to select members of the population. (every nth person is selected)
What is Systematic Sampling?
You want to find out what each students' favorite subject is. You divide a school population into groups based on grade level and then create a sample by randomly selecting students from each grade level.
What is Stratified Random Sampling?
I want to know what students in Houston County schools think about the length of class. I choose to ask middle school students and conclude they love the length of class, but wish lunch was longer. The likely type of bias is...
What is Undercoverage.