AP Statistics Unit 2: Collecting Data Vocabulary

Vocabulary flashcards covering sampling methods, statistical bias, experimental design, and scope of inference from AP Statistics Unit 2.

Bias

A characteristic of a sampling method that consistently underestimates or consistently overestimates a population parameter.

Simple Random Sample (SRS)

A sampling method in which every individual and every group of individuals in the population has an equal chance of being selected.

Convenience Sample

A non-random sampling method that selects individuals who are easiest to reach, often leading to a non-representative sample.

Voluntary Response Sample

A sampling method where a general invitation is extended to a population and individuals choose whether or not to respond.

Stratified Random Sample

A sampling method where the population is divided into subgroups (strata) based on shared characteristics, and a simple random sample is taken from each subgroup.

Strata

Groups of individuals in a population that share similar attributes or characteristics.

Cluster Sample

A sampling method where the population is classified into location-based groups (clusters), a simple random sample of clusters is selected, and all individuals within chosen clusters are sampled.

Clusters

Groups of individuals in a population located near each other that ideally mirror the diversity of the entire population.

Systematic Random Sample

A sampling method where a starting individual is chosen at random and every $k^{\text{th}}$ member of the population is selected at equal intervals.

Undercoverage

A sampling problem occurring when some groups or individuals in the population are less likely to be chosen or are completely left out of the sampling process.

Nonresponse Bias

A sampling problem that occurs when individuals chosen for a sample cannot be reached or refuse to participate.

Response Bias

A pattern of inaccurate responses caused by problems in the data gathering process, such as leading question wording or self-reported lying.

Observational Study

A study in which data are gathered by observing individuals without imposing any treatment, preventing conclusions about causation.

Experiment

A study in which treatments are intentionally imposed on experimental units to measure responses and establish cause-and-effect relationships.

Explanatory Variable

The factor manipulated by researchers in an experiment to observe its effect on an outcome variable.

Response Variable

The outcome variable measured in a study or experiment.

Confounding Variable

A variable related to the explanatory variable that influences the response variable, making it impossible to separate its effect from the explanatory variable.

Experimental Units

The individuals, animals, or objects to which treatments are applied in an experiment.

Treatment

A specific condition applied to experimental units in an experiment, representing a level or combination of levels of explanatory variables.

Control Group

A treatment group in an experiment that receives a baseline treatment, placebo, or no treatment to serve as a comparison group.

Replication

The experimental practice of assigning multiple experimental units to each treatment group so treatment differences can be distinguished from chance.

Placebo Effect

The phenomenon where subjects exhibit a measurable response or improvement after receiving a dummy or fake treatment.

Single-Blind Experiment

An experiment in which either the subjects or the individuals measuring the response variable do not know which treatment was assigned.

Double-Blind Experiment

An experiment in which neither the subjects nor the individuals evaluating outcomes know which treatment each subject received.

Block

A group of experimental units known before an experiment to be similar in a characteristic expected to affect the response variable.

Randomized Block Design

An experimental design in which subjects are separated into blocks of similar units and treatments are randomly assigned within each block.

Matched Pairs Design

A special block design using blocks of size $2$, where similar subjects are paired and randomly assigned to treatments, or each subject receives two treatments in random order.

Scope of Inference (Random Sampling)

The statistical principle stating that taking a random sample allows survey conclusions to be generalized to the broader population from which the sample was drawn.

Scope of Inference (Random Assignment)

The statistical principle stating that randomly assigning experimental units to treatments allows researchers to draw cause-and-effect conclusions.

FRAPPY

An acronym for Free Response AP Problems, Yay!, representing a process using past AP free-response questions to strengthen conceptual understanding and communication.