AP Stats Chapter 4 Vocab

Population

entire group of individuals we want info about

Census

collects data from every individual in the population

Sample

subset of individuals in the population from which we collect data

Sample survey

a study that collects data from a sample that is chosen to represent a specific population

Convenience sampling

selects individuals from a population who are easy to reach

Bias

likely to underestimate or overestimate the value you want to know

Voluntary response sampling

allows people to choose to be in the sample by responding to a general invitation

Undercoverage

random sampling from the wrong group

Simple random sample (SRS)

SRS of size n is chosen in such a way that every group of n individuals in the population has an equal chance to be selected as the sample

Observational Study

observes individuals and measures variables of interest but does not attempt to influence the responses

Response Variable

measures an outcome of a study

Explanatory Variable

helps explain or predict changes in a response variable

Confounding

occurs when two variables are associated in such a way that their effects on a response variable cannot be distinguished from each other

Experiment

deliberately imposes some treatment on individuals to measure their responses

Placebo

treatment that has no active ingredient, but is otherwise like other treatments

Treatment

specific condition applied to individuals in an experiment

Experimental unit

object to which a treatment is randomly assigned

Subject

human experimental unit

Factor

a variable that is manipulated and may cause a change in the response variable

Levels

different values of a factor

Control group

used to provide a baseline for comparing the effects of other treatments

Placebo effect

describes the fact that some subjects in an experiment will respond favorably to any treatment, even an inactive treatment

Double-blind experiment

neither the subjects nor those who interact with them and measure the response variable know which treatment a subject received

Single-blind experiment

either the subjects don't know which treatment they are receiving or the people who interact with them and measure the response variable don't know which subjects are receiving which treatment

Sampling variability

the natural difference in results you get when you take multiple samples from the same population

block

group of experimental units that are similar

Randomized block design

separate subjects into blocks and then randomly assign treatment within each block

Matched pairs design

subjects are paired (block size of 2) and then randomly assigned to a treatment

(Each subject receives two treatments order of treatments must be randomized)

Statistical Significance

the results of a study are statistically significant if they are very unlikely to happen just by chance