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 attaches a QR code at the bottom of each receipt for customers to complete, if interested.
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?
Apple is doing a giveaway at their store for the new iPhone. They select the first 100 people to come to their store to win the iPhone. They then give them an exit survey to complete. The type of bias likely present on the survey is...
What is Convenience Sampling.
The occurs when a segment of a population is either completely excluded or inadequately represented in a study's sample.
What is undercoverage (bias)?
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 groups and entire groups 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 track coach needs people to stay after school to run extra laps so they can record the times down. Only one person was able to stay 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 and Overestimation (because a slower run would take longer).
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 only members of the population who are easily accessible are chosen.
What is Convenience Sampling?
A Ph.D. student is looking for research participants for her dissertation. She decides to recruit the subjects of her study by asking students on campus if they would be willing to sit down for an interview.
What is Convenience Sampling?
A custodian asked, "Were you been messy and left food all over the lunchroom which is very inconsiderate." All students responded "no", so the 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.
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.