Samples
What is a simple random sample?
A subset of individuals chosen from a larger population where each individual has an equal chance of being selected
What is undercoverage?
Some groups in the population are left out of the sampling process.
What is a treatment?
A condition applied to subjects in an experiment.
What is an observational study?
A study where researchers observe without influencing responses.
What is inference?
Drawing conclusions about a population based on a sample.
What is a stratified random sample?
Population is divided into groups, then randomly sampled within each.
What is response bias?
When respondents answer untruthfully or misleadingly.
What is the purpose of a control group?
To provide a baseline for comparison.
What is the difference between an experiment and a survey?
Experiments impose treatments; surveys gather opinions or data.
What is the purpose of randomization?
To reduce bias and create comparable groups.
What is a cluster sample?
Entire groups are randomly selected; all members of chosen groups are surveyed.
Give one way to reduce nonresponse.
Follow up with nonrespondents or offer incentives.
Explain random assignment in experiments.
Subjects are assigned to groups by chance to reduce bias.
When is an experiment better than an observational study?
When trying to determine cause and effect.
What’s the difference between population and sample?
Population is the entire group; sample is a subset.
How does bias affect sampling results?
It leads to results that do not reflect the population accurately.
Why does question wording matter?
Poor wording can lead to biased or misunderstood responses.
What is replication in experimental design?
Using enough subjects to reduce variability in results.
Why might an experiment not be feasible?
Ethical concerns or practical limitations.
What is the goal of blocking in an experiment?
To control for known sources of variability.
Why is a representative sample important?
It ensures results can be generalized to the population.
What are the 3 main sources of bias in surveys?
Undercoverage, nonresponse, and response bias.
Describe the 3 principles of a well-designed experiment.
Control, randomization, and replication.
Give an example of each study type.
Survey – polling voters; Experiment – testing a new drug.
Explain completely randomized vs randomized block design.
Completely randomized: assign all subjects randomly. Block: group by similar traits, then randomize within each block.