AP Stat Unit 4

observational study

observe individuals and collect data without any interference with conditions

what are the two different types of observational studies

retrospective and prospective

Retrospective observational study

an observational study that has already occured

prospective observational study

an observational study being studied as it ocurs

experiment

deliberately impose some treatment on individuals to observe their responses

confounding variable

things that get in the way

simulation

mimic a situation and is alternative method for producing data when it may not be possible to carry out the experiment

population

the entire group from which you want to collect data

sample

part of the population that is actually examined

sampling

involves studying a part in order to obtain information about the whole group

census

when every member of the population is accounted for

response variable

measure the outcome of the study

explanatory variable

acounts for predicts and explains changes in the response variable

simple random sample

every possible set of n size individuals has an equal chance of being selected

stratified random sample

1st divide population into groups then perform SRS on each strata

another word for groups

strata

systematic sample

1st person is selected then each nth member after that

multi-stage

divide the population into groups, randomly select a group and survey all members of that group

convenience

sample based on avaliability

Errors that lead to bias:

confounding variables, under-coverage, non response, voluntary response, and response bias

undercoverage

when an entire group is excluded and not represented and did not have the opportunity to be included

non response

when someone is chosen to participate and chooses not to

voluntary response

people who chose to participate

response bias

respondents lie within answers

What do greek letters usually stand for?

an entire population

What do symbols typically stand for?

a specific sample

sampling frame

the list of individuals from which a sample is actually selected

What are the three principles of experimental design and explain each of them.

control: by comparing different treatment you can control outside influences

randomization: makes more impersonal which decreases bias

replication: repetition of experiments decreases variation

blocking

relates to a design of an experiment (randomize within each block) reduces variation!

experimental units

what or who you are performing the experimentation people are usually known as subjects

factors

are explanatory variable

level

when different values of an explanatory variable are used

treatment

condition being applied to the experimental unit (#factors)(#levels)=#of treatments