AP STATS PACKET

population

an entire group of individuals we want information about

census

collects data from every individual in a population

sample

subset of individuals in the population from which data is collected

sample survey

collects data from a sample to learn about the population from which the sample was collected

Random sampling

sampling that uses chance to determine which members of a population are chosen for the sample

observational study

a study that observes individuals and measures variables, but does not influence responses

retrospective

a type of observational study that examine existing data for a sample

prospective

a type of observational study that tracks the sample into the future

experiments

a study that manipulate treatments on experimental units to measure responses

simple random sampling (SRS)

sampling in such a way that every individual in the population has an equal chance to be selected

sampling without replacement

sampling in which an individual can only be selected once

sampling with replacement

sampling in which an individual can be selected more than once

cluster

a group of individuals in the population that are located near eachother

cluster sample

a sample made by randomly selecting clusters of individuals

systemic random sampling

a sample by ordered arrangement. For example, by randomly selecting k individual then every kth individual therafter.

convenience sample

a sample that consists of individuals form the population who are easy to reach

bias

underestimation and overestimation are indicative of statistical bias

voluntary response sample

a sample that consists of people who choose to be in the sample

undercoverage

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

nonresponse

when individuals chosen for the sample cannot be contacted or refuse to participate

response bias

occurs when there is a consistent pattern of inaccurate responses to a survey question

response variable

measures an outcome of a study

explanatory variable

may help explain or predict changes in a response variable

confounding

when two or more variables are associated in such a way that their effects on the response variable cannot be distinguished from eachother

treatment

a specific condition applied to the individuals in an experiment

experimental unit

the object to which a treatment is randomly assigned

placebo

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

factor

a type of explanatory variable that is manipulated and may change the response variable

levels

different values of a factor

control group

a group used to provide a baseline for comparing the effects of other treatments. For example, they may be given a placebo or no treatment at all

placebo effect

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

double blind

a type of experiment that blinds both the subjects and those who interact with them to the treatment the subjects will be receiving

single blind

a type of experiment that blinds the subject to what treatment they will be receiving

random assignment

treatments are assigned to experimental units using a chance process

completely randomized design

experimental units are assigned to the treatments completely at random

replication

giving each treatment to enough experimental units so that a difference in the effects of the treatments can be distinguished from chance variation due to random assignment

control

keeping other variables constant for all experimental units

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 pairs design

common experimental design for comparing two treatments that uses blocks of size 2.