AP Statistics Unit 4 Vocabulary

The whole entire unit 4 vocabulary.

Census

Census

Every single person in the population.

Sample survey

A Study that collects data from a sample that is chosen to represent a certain population.

Convenience Sampling

Selects individuals from the population who are easy to reach.

Bias

If its likely to under/over estimate the value needed.

Voluntary Response Sampling

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

Random Sampling

Involves using a chance process to determine which members of a population are included in the sample.

Simple Random Sample (SRS)

A 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.

Strata

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

Stratified Random Sampling

Selects sample by choosing an SRS from each stratum and combining the SRSs into one overall sample.

Clusters

Group of individuals in the population that are located near each other.

Cluster sampling

Selects sample by randomly choosing clusters and including each member of the selected clusters in the sample.

Undercoverage

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

Nonresponse

Occurs when an individual chosen for the sample cant be contacted or refuses to participate.

Response bias

Occurs when there is a systematic pattern of inaccurate answers to a survey question.

Observational study

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

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

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

Treatment

A specific condition applied to the individuals in an experiment.

Experimental unit

Object to which a treatment is randomly assgined.

Subjects

Humans in an experiment.

Factors

Variables that are manipulated and may cause a change in the response variable.

Levels

Different levels of factors.

Control group

Baseline for comparing the effects of other treatment.

Placebo Effect

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

Double Blind

Neither subjects nor those interact with them and measure the response variable will know which treatment a subject received.

Single Blind

One person whether its the person receiving or giving the treatment dont know who is getting the treatment.

Random Assignment

Experimental units are assigned to treatments using a chance process.

Control

Keeping other variables constant for all experimental units.

Replication

Using enough experimental units to distinguish a difference in the effects of the treatment from chance variation due to the random assignment.

Completely Randomized Design

The experimental units are assigned to the treatments completely by chance.

Block

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.

Randomized Block Design

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

Matched Pairs Design

Experimental units are paired by similarity and the two treatments used are randomly assigned in each pair.

Sampling Variability

Refers to the fact that the random samples from the same size produces different estimates. (just because a study proved something, doesnt mean its true for all)

Statistically Important

When observed results of a study are too unusual to be explained by chance alone. (having a cause and effect, NOT by chance)

Random Selection

Helps bias and produces reliable estimates about a study.

Random Assignment

Helps ensure two groups of subjects are as alike as possible before the treatments are imposed.

Institutional Review Board

Ensures safety and nature of a study. Not to decide if a study will produce valuable data.

Informed Consent

Informing the subjects before hand about the nature and risk of the study. Written consent is required. (time consumption and emotional risk)

Confidentiality

Protects individual’s privacy. This doesn’t mean anonymity. Anonymity is rare. Confidentiality allows follow up in nonresponse or to inform results.