Definitions
What is a subset of a population used for research?
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...
"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.
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...
Voluntary Response Bias
What are all members of a group that you are looking to make generalizations about called?
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...
"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 how the car riders are dismissed. She surveys car riders from the following: girls from 4 grade and the boys from 5th grade.
Stratified Sampling
I ask my students "What do you think of this incredibly fun jeopardy game?"
Response Bias
What is a selection process in which every item has an equal probability of being chosen?
Simple Random Sample (SRS)
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...
"the 40 threaded rods selected"
The sampling method in which the population is divided into subgroups?
What is Stratified 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.
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. So, he surveys only students on the football team.
Undercoverage
What is the sample method where you first divide your population into subgroups of similar categories?
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...
"the occupants of all seats in the stadium"
The sampling method where the researcher picks whoever they see first.
Convenience
A Ph.D. student is looking for research participants for her dissertation. She decides to recruit the first 10 students she sees.
Convenience Sample
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.
Response Bias
What is a sample that is NOT representative of the population it was drawn from?
Biased
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...
"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 visit 10 different classrooms and survey all the students only in those classes.
Cluster Sample
Bias or Fair?
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. Then asked the teachers at one middle school.
Bias