AP Statistics Chapter 4 Designing studies Vocabulary Terms

Population

a group of existing objects (e.g. the set of all stars within the Milky Way galaxy) or a hypothetical and potentially infinite group of objects conceived as a generalization from experience (e.g. the set of all possible hands in a game of poker).

Census

the complete enumeration of a population or groups at a point in time with respect to well defined characteristics: for example, population, production, traffic on particular roads.

sample survey

a study that asks questions of a sample drawn from some population in the hope of learning something about the entire population

sample

a subset of the population

Convenience sample

only members of the population who are easily accessible are selected

bias

prejudice in favor of or against one thing, person, or group compared with another, usually in a way considered to be unfair.

Voluntary Response Sample

A sample which involves only those who want to participate in the sampling

random sampling

a sample that fairly represents a population because each member has an equal chance of inclusion

simple random sample

every member of the population has a known and equal chance of selection

stratified random sample

a sample from selected subgroups of the target population in which everyone in those subgroups has an equal chance of being included in the research

Strata

layers

cluster sample

obtained by selecting all individuals within a randomly selected collection or group of individuals

cluster

A number of similar things grouped together

Undercoverage

occurs when some groups in the population are left out of the process of choosing the sample

non-response bias

bias introduced to a sample when a large fraction of those sampled fails to respond

response bias

anything in a survey design that influences responses

wording of questions

The most important influence on the answers given to a survey. Confusing or leading questions can introduce strong bias, and changes in wording can greatly change a survey's outcome. Even the order in which questions are asked matters.

Observational study

research that gathers data in a real-world setting without intentionally manipulating any variable

experiment

A research method in which an investigator manipulates one or more factors to observe the effect on some behavior or mental process

confounding variable

in an experiment, a factor other than the independent variable that might produce an effect

Treatment

a specific condition applied to the individuals in an experiment

experimental units

individuals on whom an experiment is performed

Subjects

individuals who are obliged to submit to a government authority against which they have no rights

Factors

the explanatory variables in an experiment

levels

the specific values that the experimenter chooses for a factor

Comparison

Examination of two or more objects with reference to their likeness or unlikeness.

Random assignment

assigning participants to experimental and control groups by chance, thus minimizing preexisting differences between those assigned to the different groups

Control

standard for comparison

Replication

repeating the essence of a research study, usually with different participants in different situations, to see whether the basic finding extends to other participants and circumstances

Completely randomized design

When the treatments are assigned to all the experimental units completely by chance.

blinding

any individual associated with an experiment who is not aware of how subjects have been allocated to treatment groups

double-blind procedure

an experimental procedure in which both the research participants and the research staff are ignorant (blind) about whether the research participants have received the treatment or a placebo. Commonly used in drug-evaluation studies.

statistically significant

an observed effect so large that it would rarely occur by chance at least 5% correlation.

blocking

Different groups receiving different treatments

Block

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

randomized block design

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

Matched pair design

a design in which one creates a set of two participants who are highly similar on a key trait and then randomly assigns individuals in the pair to different groups

placebo

something which has a positive mental effect, but no physical effect

placebo effect

the phenomenon in which the expectations of the participants in a study can influence their behavior

cause and effect

A relationship in which change in one variable causes change in another

lack of realism

When the treatments, the subjects, or the environment of an experiment are not realistic. Lack of realism can limit researchers' ability to apply the conclusions of an experiment to the settings of greatest interest.

informed consent

An ethical principle requiring that research participants be told enough to enable them to choose whether they wish to participate.

Confidential

communicated in trust; secret; private