Types of Samples and Collecting Data Methods

Random

Each member of a population has an equal chance of being selected. Most likely to be representative of a population

Ex. Put every student’s name in a hat and pull out 100 names.

Self-selected

Members of a population can volunteer to be in the sample.

Ex. Send an email with a school improvement survey to parents and use the surveys that are returned.

Systematic

A rule is used to select members of a population

Ex. Select every other person

Stratified

A population is divided into smaller groups that share a similar characteristic. A sample is then randomly selected from each group.

Ex. Divide the students up based on what math class they take. Pick 20 students from each course and ask them your questions.

Cluster

A population is divided into groups called clusters. All of the members in one or more of the clusters are selected.

Ex. Divide the students up based on what math class they take. Pick one class and ask all of the students in the class.

Convenience

Only members of a population who are easy to reach are selected.

Ex. Ask the students that you eat lunch with your survey questions

Experiment

Applying a treatment on subjects and observing the effect.

Ex. A doctor splits up a group of people and gives them a new medicine to try while the others stay on their current medicine.

Observational Study

Observing and measuring specific characteristics without controlling the individuals or their environment.

Ex. MDOT randomly selects semi-trucks and weighs them at a truck weighing station

Survey

An investigation of one or more characteristics of a population

Ex. A poll is taken to see the percentage of voting American adults that approve of the current president.

Simulation

Uses a model to reproduce the conditions of a situation or process so that the simulated outcomes closely match the real-world outcomes.

Ex. A manager uses a computer program to predict how many defective products can be expected on a particular assembly line

Parameter

A number that represents the population

Statistic

A number that represents the sample.