Module 1: Thinking Statistically and Collecting Data

Cluster sampling

Divides a population into groups via some criterion, then uses simple random selection or systematic selection to select one or more groups as the sample.

Convenience sampling

A sample of individuals who are most accessible to the researcher. A convenience sample is usually not random or representative of the population.

Data

Factual information about a group of individuals, animals, or objects.

Informed consent

Risks of participation must be clearly explained to the subjects of the study.

Non-response bias

When an individual chosen for a sample cannot be contacted or decides to not participate in the study or research.

Observational units

The group of individuals, animals, or objects in the study.

Parameter

A numerical summary measure that summarizes that population.

Population

An entire group of people, objects, or animals; usually a large group.

Response bias

A systemic pattern of inaccurate responses to questions.

Sample

A randomly selected subset or subgroup of a population.

Sampling bias

When a sample is collected from a population and some members of the population are not as likely to be chosen as others.

Simple random sample

A random mechanism to choose a sample, without replacement, from the population so that every sample of a given size has the same chance of being selected.

Statistic

A numerical summary measure of a sample.

Statistical investigative question

A question that can be used as the starting point for an investigation that involves data collection and data analysis.

Stratified sampling

A population is divided into two or more groups according to some criterion, and a sample is selected from each strata using simple random sampling or systematic sampling.

Survey question

Questions researchers ask in order to collect data, which is expected to vary from individual to individual.

Systematic sampling

Every individual in the population is given a number and individuals/entities are chosen at regular intervals, with a random starting point.

Qualitative/categorical data

Categorizing or describing attributes of a population.

Quantitative continuous data

Data that are not only made up of counting numbers, but that may include fractions, decimals, or irrational numbers.

Quantitative discrete data

Data that can take on only certain numerical values.

Unbiased

A representative sample of the population.

Undercoverage

When some groups of the population are left out of the sampling process and the individuals in these groups do not have an equal chance of being selected for the sample.

Variables

The characteristics of observational units.

Variability

The variance between data points.

Voluntary response bias

People who volunteer for a study or survey may be more inclined to respond to questions or report certain behaviors.