AP Stats Unit 2

Census

Collects data from every individual in the pop

Sample survey

Collects data from the sample to learn about the population

Convenience sampling

Collects individuals from a population that are easy to reach

Voluntary response sampling

Allows people to choose to be in the sample by general invitation

Simple Random Sample (SRS)

A sample where every individual has an equal chance of being selected from the population.

Sampling with replacement

An individual can be selected more than once

Sampling without replacement

An individual can NOT be selected more than once

Strata

Individuals within a population that share similar characteristics, used in stratified sampling.

Stratified random sampling

A sampling method where the population is divided into strata, and random samples are taken from each stratum to ensure representation of all characteristics.

Cluster

A group of individuals in a population located near each other

Cluster Sampling

Population is divided into clusters, and the entire clusters are randomly selected for sampling.

Systematic random sampling

A sampling method where individuals are selected at regular intervals from a predetermined starting point in a population list.

Undercoverage

A sampling error that occurs when some members of the population are inadequately represented in the sample, leading to biased results.

Nonresponse

A type of sampling error that occurs when individuals chosen for the sample do not respond or participate, which can lead to biased results.

Response bias

A type of error that occurs when respondents provide inaccurate or untruthful answers, which can distort the results of a survey or study.

Extraneous Variable

Can influence the outcome of a study, potentially confounding the results.

Confounding Variable

Effects both the input and output of a study leading to innacurate results

Explanatory Variable

A variable that is manipulated or observed in a study to determine its effect on a response variable.

Observational Study v.s. Experiment

Observational Study includes no treatments and letting subjects choose, while Experiments impose treatments.

Experimental Units (Subjects)

Who/what the treatment is being imposed on

Placebo effect

A phenomenon where participants experience a perceived improvement in their condition due to their expectations, rather than the treatment itself.

Single Blind Study

A study in which participants are unaware of whether they are receiving the treatment or a placebo, but the researchers know.

Double Blind Study

A study in which neither the participants nor the researchers know who is receiving the treatment or a placebo, helping to eliminate bias.

Control Group

A group of participants in an experiment that does not receive the treatment or intervention, used as a benchmark to measure the effects of the treatment.

How to explain a Random Assignment

1. Label

2. Randomize

3. Assign

What does a well Designed Experiment have?

Comparison, Random Assignment, Replication, and a Control group

Replication

Repeating an experiment to confirm results and ensure reliability.

Block Design