STATS UNIT 1

Individual

A person, object, or event that provides data.

Variable

A characteristic of an individual that can vary.

Population

The entire group of individuals of interest.

Sample

A portion of the population used in a study.

Sample Size

The number of individuals in the sample.

Parameter

A numerical characteristic of a population; fixed but usually unknown.

Statistic

A numerical characteristic of a sample; used to estimate a parameter.

Qualitative Data

Non-numeric, categorical data.

Quantitative Data

Numeric data.

Discrete Data

Countable numeric data; no decimals possible.

Continuous Data

Measured numeric data; decimals possible.

Observational Study

A study where researchers do not influence individuals; they only observe and record data.

Experimental Study

A study where researchers apply a treatment to affect individuals' responses.

Treatment

A condition applied to individuals in an experiment.

Control Group

The group that does not receive the treatment.

Experimental Group

The group that receives the treatment.

Randomization

Random assignment of subjects to groups to reduce bias.

Completely Randomized Design

Individuals are randomly assigned to control and experimental groups.

Randomized Block Design

Individuals are first grouped into blocks based on a characteristic, then randomly assigned to treatments within each block.

Block

A group of individuals sharing a characteristic relevant to the study.

Matched-Pairs Design

Individuals are paired based on similarity, and each individual in the pair receives a different treatment.

Simple Random Sample (SRS)

Every possible sample of size n has an equal chance of being selected.

Cluster Sample

Population divided into non-overlapping groups; entire clusters are randomly selected and surveyed.

Stratified Random Sample

Population divided into non-overlapping groups (strata) based on a characteristic, then random samples are taken from each group.

Systematic Sample

Choose a random starting point, then select every kth individual.

Voluntary Response Sample

Only individuals who choose to respond participate.

Convenience Sample

Individuals selected because they are easy to access.

Under-coverage

Some groups in the population are left out of the sampling process.

Nonresponse

Selected individuals do not respond or cannot participate.

Small Sample Bias

A sample too small to represent a diverse population.

Missing Data

When subjects do not provide all requested information or drop out of a study.

Priming / Ordering Bias

Question wording or order encourages certain answers.