AP Stats Test 4

collects data from every individual in the population

Census

occurs when 2 variables are associated in such a way that their effects on a response variable cannot be distinguished from each other

Confounding

may help explain or predict changes in a response variable

Explanatory Variable

in an experiment, it is a variable that is manipulated and may cause a change in the response variable

Factor

different values of a factor

Levels

measures the outcome of a study

Response Variable

In an experiment, an observed effect so large that it would rarely occur by chance is called

Statistically Significant

groups of individuals in a population who share characteristics thought to be associated with the variables being measured in a study

Strata

selects a sample by choosing an SRS from each stratum and combining the SRS's into one overall sample

Stratified Random Sampling

occurs when some members of the population are less likely to be chosen or cannot be chosen in a sample

Undercoverage

a group of experimental units that are known before the experiment to be similar in some way that is expected to affect the response to the treatments

Block

a group of individuals in the population that are located near each other

Cluster

selects a sample by randomly choosing clusters and including each member of the selected clusters in the sample

Cluster Sampling

4 Principles of Experimental Design

Comparison, random assignment, control, replication

The reason that blocking (as in randomized block design) is sometimes used in experimentation is to

Compensate for anticipated differences in the response variable for different values of a specified "blocking" variable

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

Double-Blind Experiment

What is the principle purpose of control in a randomized comparative experiment?

Isolating the effect of the treatment variable by keeping all other variables the same in the treatment groups

common design for comparing two treatments that uses blocks of size 2. Some 2 very similar experimental units are paired and the two are randomly assigned within each pair. In others, each experimental unit receives both treatments in a random order.

Matched Pairs

occurs when individual chosen for the sample can't be contacted or refuses to participate

Nonresponse

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

Placebo

random assignment of experimental units to treatments carried out separately within each block

Randomized Block Design

Using enough experimental unites to distinguish a difference in the effects of the treatments from chance variation due to the random assignment

Replication

The theory proposes that some voters tend to tell pollsters they are undecided or likely to vote for a non-white candidate, and yet, on election day, vote for the white opponent. This is an example of what?

Response Bias

a 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

Simple Random Sample (SRS)

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

Single-Based Experiment

Viewers phoning in is an example of which sample

Voluntary Response

A stratified random sample is appropriate when

the population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is very similar within the groups but quite different between the groups