AP Statistics Unit 3 Vocabulary

population

entire group of individuals we want information about

sample

group within population from which we actually collect data from

census

collect data from every individual in the population

sample survey

study that uses an organized plan to choose a sample that represents some specific population, basing conclusions about the population on data from the sample

bias

design of a statistical study that consistently underestimates or overestimates value you would want to know

convenience sample

sample selected by taking from the population individuals that are easy to reach

voluntary response

people deciding whether to join a sample by responding to an invitation

simple random sample

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

random sampling

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

hat method

place all names in an EQUAL slip of paper and randomly select names, rep/no rep

technology

random digit table

stratified random sample

sample obtained by classifying the population into groups of similar individuals, choosing separate SRS in each stratum and combining these SRSs to form the sample.

strata

classifying population into groups of similar individuals

cluster random sample

sample obtained by classifying the population into groups of individuals that are located near each other, called clusters, then choosing an SRS of the clusters.

systematic random sampling

randomly choosing a selected, repeated interval

margin of error

how much you can expect your survey results to reflect the views from the overall population

undercoverage

occurs when some members of the population cannot be chosen in a sample

nonresponse bias

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

wording of questions

important influence on answers given in a survey; confusing/leading questions can introduce strong bias and change a survey's outcome. can also include question order asked

errors in design methods

convenience sampling / voluntary response sampling (designer's flaws)

errors causing response bias

undercoverage, nonresponse, wording of questions

observational study

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

experiment

study in which researchers deliberately impose treatments on individuals to measure their responses

confounding

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

well-designed experiment

control group

experiment group whose primary purpose is to provide a baseline for comparing the effects of the other treatments. depending on the purpose of the experiment, a placebo or active treatment can be administered

treatment

specific condition applied to the individuals in an experiment. if an experiment has several explanatory variables, a ______ is a combination of specific values of these variables

experimental units

smallest collection of individuals to which treatments are applied

subject

experimental units that are human beings

factor

explanatory variables in an experiment

level

specific value of an explanatory variable in an experiment

experimental variable

variable that may help or explain or predict changes in a response variable

response variable

variable that measures an outcome of a study

completely randomized design

design in which the experimental units are assigned to the treatments completely by chance

replication

experimental design principle; use enough experimental units in each group so that any differences in the effects of the treatments can be distinguished from chance differences between the groups

control

experimental design principle that mandates keeping other variables that might affect the response the same for all groups.

single-blind

experiment which either the subjects or those who interact with them and measure the response variable, but not both, know which treatment a subject is received

double blind

both the researchers and participants neither know which treatment is being administered

principles of experimental design

control, randomization, blocking, replication

matched pairs

common form of blocking for comparing just two treatments, both subjects receive both treatments or subjects are matched in pairs as closely as possible and each subject is in a pair randomly assigned to receive one of the treatments.

blocking

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

randomized block design

scope of inference

lack of realism

when the treatments, subjects, or the environment of an experiment are not realistic; limit researcher's ability to apply the conclusions of an experiment to the settings of greatest interest