Understanding Surveys, Experiments, and Observational Studies - Statistics
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What is the primary purpose of an experiment in statistics?
What is the primary purpose of an experiment in statistics?
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Test for cause-and-effect by imposing treatments. Experiments manipulate variables to establish causal relationships.
Test for cause-and-effect by imposing treatments. Experiments manipulate variables to establish causal relationships.
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What is the primary purpose of a sample survey in statistics?
What is the primary purpose of a sample survey in statistics?
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Estimate population characteristics using data from a sample. Surveys use samples to make inferences about larger populations.
Estimate population characteristics using data from a sample. Surveys use samples to make inferences about larger populations.
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What is the primary purpose of an observational study in statistics?
What is the primary purpose of an observational study in statistics?
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Describe associations by observing without assigning treatments. Observational studies measure without intervention or manipulation.
Describe associations by observing without assigning treatments. Observational studies measure without intervention or manipulation.
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Which study type can justify a cause-and-effect conclusion when well designed?
Which study type can justify a cause-and-effect conclusion when well designed?
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A randomized experiment. Only experiments with random assignment can establish causation.
A randomized experiment. Only experiments with random assignment can establish causation.
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Which study type is best for estimating a population proportion or mean?
Which study type is best for estimating a population proportion or mean?
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A sample survey with a random sample. Random sampling ensures the sample represents the population.
A sample survey with a random sample. Random sampling ensures the sample represents the population.
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What key feature distinguishes an experiment from an observational study?
What key feature distinguishes an experiment from an observational study?
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The researcher assigns treatments in an experiment. Experiments control treatments; observational studies don't.
The researcher assigns treatments in an experiment. Experiments control treatments; observational studies don't.
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What does random sampling help prevent in a sample survey?
What does random sampling help prevent in a sample survey?
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Selection bias (unrepresentative samples). Random sampling ensures all population members have equal selection chance.
Selection bias (unrepresentative samples). Random sampling ensures all population members have equal selection chance.
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What does random assignment help prevent in an experiment?
What does random assignment help prevent in an experiment?
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Confounding by balancing lurking variables across groups. Random assignment distributes unknown factors equally between groups.
Confounding by balancing lurking variables across groups. Random assignment distributes unknown factors equally between groups.
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What is a confounding variable?
What is a confounding variable?
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A variable related to both the explanatory and response variables. Confounders create false associations between variables.
A variable related to both the explanatory and response variables. Confounders create false associations between variables.
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What is a lurking variable?
What is a lurking variable?
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An unmeasured variable that affects the response variable. Lurking variables are hidden factors that influence outcomes.
An unmeasured variable that affects the response variable. Lurking variables are hidden factors that influence outcomes.
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Which option best describes random sampling: selecting units or assigning treatments?
Which option best describes random sampling: selecting units or assigning treatments?
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Selecting units from a population by chance. Random sampling chooses who participates from the population.
Selecting units from a population by chance. Random sampling chooses who participates from the population.
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Which option best describes random assignment: selecting units or assigning treatments?
Which option best describes random assignment: selecting units or assigning treatments?
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Assigning subjects to treatment groups by chance. Random assignment determines which treatment each subject receives.
Assigning subjects to treatment groups by chance. Random assignment determines which treatment each subject receives.
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Identify the study type: A poll contacts $1000$ voters chosen at random from a voter list.
Identify the study type: A poll contacts $1000$ voters chosen at random from a voter list.
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Sample survey (random sample). Random selection from voter list indicates a sample survey.
Sample survey (random sample). Random selection from voter list indicates a sample survey.
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Identify the study type: Patients are randomly assigned to drug or placebo, then outcomes are compared.
Identify the study type: Patients are randomly assigned to drug or placebo, then outcomes are compared.
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Randomized experiment. Random assignment to treatments defines an experiment.
Randomized experiment. Random assignment to treatments defines an experiment.
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Identify the study type: Researchers record diet and blood pressure with no assigned diet plan.
Identify the study type: Researchers record diet and blood pressure with no assigned diet plan.
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Observational study. No treatment assignment means it's observational.
Observational study. No treatment assignment means it's observational.
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Which conclusion is justified: causation or association, from a well-designed observational study?
Which conclusion is justified: causation or association, from a well-designed observational study?
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Association only (not causation). Without random assignment, causation cannot be established.
Association only (not causation). Without random assignment, causation cannot be established.
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Which conclusion is justified: causation or association, from a randomized experiment?
Which conclusion is justified: causation or association, from a randomized experiment?
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Causation (if the experiment is well designed). Random assignment allows causal conclusions.
Causation (if the experiment is well designed). Random assignment allows causal conclusions.
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Identify the flaw: A survey about school lunches is posted online and anyone may respond.
Identify the flaw: A survey about school lunches is posted online and anyone may respond.
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Voluntary response bias (not a random sample). Self-selected respondents don't represent the population.
Voluntary response bias (not a random sample). Self-selected respondents don't represent the population.
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Identify the flaw: A study compares two treatments, but subjects choose which treatment to take.
Identify the flaw: A study compares two treatments, but subjects choose which treatment to take.
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No random assignment; confounding is likely. Self-selection introduces bias and prevents causal conclusions.
No random assignment; confounding is likely. Self-selection introduces bias and prevents causal conclusions.
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Which statement is correct: Random sampling implies random assignment, or they are independent?
Which statement is correct: Random sampling implies random assignment, or they are independent?
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They are independent; one does not imply the other. Random sampling and random assignment serve different purposes.
They are independent; one does not imply the other. Random sampling and random assignment serve different purposes.
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What is the defining feature that makes a study a sample survey rather than an experiment?
What is the defining feature that makes a study a sample survey rather than an experiment?
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Data are collected by asking/recording responses, not assigning treatments. Surveys observe existing characteristics without manipulation.
Data are collected by asking/recording responses, not assigning treatments. Surveys observe existing characteristics without manipulation.
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What does random assignment primarily help prevent in an experiment?
What does random assignment primarily help prevent in an experiment?
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Confounding; it balances lurking variables across treatment groups. Randomization distributes unknown factors evenly between groups.
Confounding; it balances lurking variables across treatment groups. Randomization distributes unknown factors evenly between groups.
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Which phrase correctly matches the idea: random selection or random assignment makes results generalizable to a population?
Which phrase correctly matches the idea: random selection or random assignment makes results generalizable to a population?
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Random selection (random sampling). Representative samples allow inference to the larger population.
Random selection (random sampling). Representative samples allow inference to the larger population.
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Which phrase correctly matches the idea: random selection or random assignment supports cause-and-effect conclusions?
Which phrase correctly matches the idea: random selection or random assignment supports cause-and-effect conclusions?
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Random assignment. Randomization controls confounding variables in experiments.
Random assignment. Randomization controls confounding variables in experiments.
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Which statement is correct: A survey with random sampling but no random assignment can establish causation?
Which statement is correct: A survey with random sampling but no random assignment can establish causation?
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No; it can generalize estimates but cannot establish causation. Surveys measure associations but can't prove one variable causes another.
No; it can generalize estimates but cannot establish causation. Surveys measure associations but can't prove one variable causes another.
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What is a confounding variable in the context of experiments and observational studies?
What is a confounding variable in the context of experiments and observational studies?
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A variable related to both explanatory and response variables that distorts conclusions. Third variables can create spurious relationships between studied variables.
A variable related to both explanatory and response variables that distorts conclusions. Third variables can create spurious relationships between studied variables.
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Which statement is correct: An experiment with random assignment but no random sampling can generalize to the whole population?
Which statement is correct: An experiment with random assignment but no random sampling can generalize to the whole population?
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No; it supports causation for subjects, not broad generalization. Without random sampling, results apply only to study participants.
No; it supports causation for subjects, not broad generalization. Without random sampling, results apply only to study participants.
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Which conclusion is justified: In an observational study, can a strong association imply causation?
Which conclusion is justified: In an observational study, can a strong association imply causation?
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No; observational studies can show association but not causation. Correlation doesn't imply causation without controlled experiments.
No; observational studies can show association but not causation. Correlation doesn't imply causation without controlled experiments.
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Identify the randomization method: Names are drawn at random from a roster to choose participants.
Identify the randomization method: Names are drawn at random from a roster to choose participants.
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Random selection (random sampling). Drawing names randomly creates a representative sample.
Random selection (random sampling). Drawing names randomly creates a representative sample.
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Identify the randomization method: Subjects are placed into treatments by flipping a fair coin.
Identify the randomization method: Subjects are placed into treatments by flipping a fair coin.
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Random assignment. Coin flip randomly allocates subjects to treatment groups.
Random assignment. Coin flip randomly allocates subjects to treatment groups.
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