AP Stats-Chapter 4

population

The entire group of individuals or instances about whom we hope to learn.

census

A survey that attempts to include the entire population.

sample

A subset of the population selected for observation and analysis.

sample survey

A method of collecting data from a sample of individuals.

convenience sampling

A sampling method that involves selecting individuals who are easiest to reach.

bias

Systematic error introduced into sampling or testing. PRODUCES DIRECTION

voluntary response sampling

A sampling method where individuals choose to participate. EX PEOPLE GO TAKE A SURVEY THEY ARE PASSIONATE ABOUT NOT SOMETHING RANDOM

random sampling (method)

A sampling method where each individual has an equal chance of being selected.

simple random sample (SRS)

A sample in which each member of the population has an equal chance of being selected.

sampling without replacement

A sampling method where selected individuals are not returned to the population.

sampling with replacement

A sampling method where selected individuals are returned to the population.

table of random digits

A table used to generate random numbers for sampling.

stratified random sample

A sampling method that involves dividing the population into strata and then taking a random sample from each stratum.

strata

Subgroups within a population that share similar characteristics.

cluster sampling

A sampling method where the population is divided into clusters and entire clusters are randomly selected.

clusters

Groups of individuals within a population.

systematic random sample

A sampling method where individuals are selected at regular intervals from a randomly ordered list.

undercoverage

A sampling error that occurs when some members of the population are inadequately represented.

nonresponse

A bias that occurs when individuals selected for a sample do not respond.

response bias

A bias that occurs when respondents provide inaccurate answers.

wording of questions

The specific phrasing of survey questions that can influence responses.

observational study

A study where researchers observe and measure outcomes without manipulating variables.

prospective

A type of observational study that follows participants forward in time.

retrospective

A type of observational study that looks back at data collected in the past.

experiment

A study in which researchers manipulate one or more variables to observe the effect on another variable.

confounding

A situation in which two variables are associated in such a way that their effects on a response variable cannot be distinguished.

placebo

A treatment that has no therapeutic effect, used as a control in experiments.

experimental units

The smallest division of experimental material such that any two units may receive different treatments.

subjects

Individuals who participate in an experiment.

treatment

The specific condition applied to the subjects in an experiment.

factor

An independent variable in an experiment.

level

The specific values that a factor can take.

control group

A group in an experiment that does not receive the treatment and is used for comparison.

placebo effect

The phenomenon where patients experience improvements in their condition simply because they believe they are receiving treatment.

double-blind experiment

An experiment in which neither the participants nor the experimenters know who is receiving a particular treatment.

single blind experiment

An experiment in which the participants do not know whether they are receiving the treatment or a placebo.

comparison

The act of evaluating two or more treatments to determine their effects.

random assignment

The process of randomly assigning participants to different treatment groups.

control

The standard against which the results of an experiment are compared.

replication

The repetition of an experiment to confirm findings.

completely randomized design

An experimental design where all subjects are assigned to treatments completely at random.

block

A group of experimental units that are similar in some way that is expected to affect the response to the treatments.

randomized block design

An experimental design that divides subjects into blocks and then randomly assigns treatments within each block.

matched pair design

An experimental design that pairs subjects with similar characteristics and assigns different treatments to each.

sampling variability

The natural variation in results that occurs when different samples are taken from the same population.

statistically significant

A result that is unlikely to have occurred by chance alone.

scope of inference

The extent to which the results of a study can be generalized to a larger population.

informed consent

The process of obtaining permission from participants after they have been informed of the study's purpose and procedures.

confidentiality

The ethical principle of keeping participant information private.

HOW TO CHOOSE A SRS

1. Label

2. Randomize - using random number generator, paper, or digi table

3. select

why is convenience sampling bad?

produces unrepresenation (easy to reach people) and bias (shows direction)

Random sampling can make you make an inference about what?

INFERENCE ABOUT POPULATION

Random assignment can make you make an inference about what?

INFERENCE ABOUT CAUSE AND EFFECT

When can you make a inference about something

If there is a treatment being administered CANNOT MAKE AN ASSUMPTIONS IF THERE IS ONLY INFORMATION AND NO TREATMENT!