Introduction to Experimental Design - AP Statistics

What is cluster sampling?

Dividing the population into groups and sampling entire groups. Samples natural groups rather than individuals.
Identify one benefit of using a matched pairs design.

Reduces variability by pairing similar units. Increases precision by controlling individual variation.
What is double blinding?

Both subjects and experimenters do not know the treatment assignments. Eliminates bias from both participants and researchers.
What is a randomized block design?

Units are blocked and then randomly assigned within each block. Combines blocking with randomization for control.
What is meant by the term 'experimental bias'?

Systematic errors in the design or conduct of an experiment. Systematic flaws that distort results.
Define interaction in experimental design.

When the effect of one factor depends on another factor. Factors combine to create different effects.
What is a confounding variable?

A variable that influences both the response and explanatory variables. Distorts true treatment effects through correlation.
Identify a key feature of a factorial design.

All combinations of factors are tested. Tests all possible factor combinations systematically.
What does 'internal validity' refer to?

The degree to which the study accurately reflects causal relationships. Measures accuracy of causal conclusions within study.
What is selection bias?

Bias introduced by the method of selecting participants. Non-representative sampling distorts results.
What is a cross-sectional study?

Observes a population at a single point in time. Snapshot of population at one moment.
What is the purpose of a pilot study?

To test procedures and identify potential problems. Preliminary trial to refine methodology.
Define a factor in experimental design.

An explanatory variable manipulated in the experiment. The independent variable controlled by researchers.
What is a longitudinal study?

Observes the same subjects over a period of time. Tracks changes in subjects over time.
Define randomization in the context of experiments.

Random assignment of treatments to experimental units. Ensures unbiased treatment allocation.
What is replication in experimental design?

Applying treatments to multiple experimental units. Increases reliability and statistical power.
Define the term 'external validity'.

Extent to which results can be generalized to other contexts. Measures generalizability beyond study conditions.
What is a treatment in an experiment?

A specific condition applied to experimental units. The experimental intervention being tested.
What is a level in the context of a factor?

A specific value or category of a factor. Different settings or values of a factor.
What is the purpose of a control in experiments?

To provide a baseline for comparison. Essential reference point for measuring treatment effects.
What is a lurking variable?

A variable that is not considered but affects the outcome. Hidden variable that may influence results.
What is a matched pairs design?

A design where units are paired, and each pair receives different treatments. Controls for individual differences effectively.
Identify a characteristic of a quasi-experiment.

Lacks random assignment of treatments. Cannot establish causation without randomization.
What is a carryover effect in experiments?

Effects of a treatment that persist into subsequent conditions. Previous treatments influence subsequent responses.
What is the placebo effect?

A change in response due to the belief in treatment efficacy. Psychological response to perceived treatment.
What is the definition of an experimental unit?

An individual or object to which a treatment is applied. The basic entity receiving experimental treatment.
What is the purpose of using a placebo in experiments?

To control for the placebo effect. Neutralizes psychological treatment responses.
What is the difference between an observational study and an experiment?

Experiments involve manipulation; observational studies do not. Key distinction is researcher control of variables.
What is the main difference between a single-blind and a double-blind experiment?

Single-blind conceals from subjects; double-blind from subjects and experimenters. Double-blind also conceals from experimenters.
What is the purpose of blinding in experiments?

To prevent bias by concealing treatment allocation. Reduces psychological and experimenter bias.
Identify the main purpose of stratified sampling.

To ensure representation across key subgroups. Maintains proportional representation across strata.
What is the Hawthorne effect?

A change in behavior due to awareness of being observed. Behavioral modification due to observation awareness.
What is a response variable?

The outcome measured to assess the effect of a treatment. The dependent variable being measured.
Identify a method to reduce experimental bias.

Implementing blinding procedures. Concealment prevents knowledge-based bias.
Identify a characteristic of a block design.

Units are grouped into blocks before treatments are assigned. Controls for variability within similar groups.
Define systematic sampling.

Selecting every $k^{th}$ individual from a list. Regular interval selection from ordered list.
What is a completely randomized design?

An experimental design where all units are randomly assigned treatments. Simple design with random treatment assignment.
Identify the main advantage of random assignment.

Reduces bias and balances confounding variables. Eliminates systematic differences between groups.
What is the primary goal of an experiment?

To determine causation between variables. Establishes cause-and-effect relationships through manipulation.
What is a control group?

A group that receives no treatment or a standard treatment. Provides baseline comparison for treatment effects.

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