AP Stats Unit 3

Population

The entire group of individuals or instances about whom we hope to learn

Sample

A subset of the population selected for study

Census

A study that attempts to collect data from every individual in the population

Sampling

The process of selecting a sample from the population

Simple Random Sample (SRS)

A sample in which every individual has an equal chance of being selected

Stratified Random Sample

The population is divided into strata, and a random sample is taken from each stratum

Cluster Sample

The population is divided into clusters, some clusters are randomly selected, and all individuals in the selected clusters are surveyed

Systematic Sample

Every nth individual is selected from a list or queue

Convenience Sample

A sample taken from a group that is easy to access

Voluntary Response Sample

A sample consisting of individuals who choose themselves by responding to a general appeal

Bias

A systematic error that leads to an incorrect estimate of the population parameter

Undercoverage

Occurs when some members of the population are inadequately represented in the sample

Nonresponse Bias

Occurs when individuals selected for the sample do not respond

Response Bias

Occurs when the behavior of the respondent or interviewer influences the response

Wording Bias

Occurs when the wording of a question influences the response

Observational Study

Observes individuals and measures variables without influencing the responses

Experiment

Deliberately imposes treatments on individuals to measure their responses

Experimental Units

The individuals on which the experiment is done

Subjects

Human experimental units

Treatment

A specific condition applied to the individuals in an experiment

Factor

An explanatory variable in an experiment

Level

A specific value of a factor

Control Group

A group that receives no treatment or a placebo

Placebo

A dummy treatment with no active ingredients

Blinding

When subjects do not know which treatment they are receiving

Double-Blind

Neither the subjects nor the experimenters know which treatment is being administered

Randomization

The use of chance to assign subjects to treatments

Replication

Repeating the experiment on many subjects to reduce chance variation

Confounding Variable

A variable that is related to both the treatment and the response and may influence the outcome

Blocking

Grouping similar experimental units together and then randomly assigning treatments within each block

Matched Pairs Design

A design where pairs of subjects are matched and then randomly assigned different treatment