Sampling methods

Voluntary sample

A group of people who choose to participate in a survey on their own.

Convenience sample

A sample composed of easily accessible individuals.

Simple random sampling

A method where all possible samples of n objects have an equal chance of being selected.

Stratified sampling

Dividing the population into groups based on a characteristic, then taking a Simple Random Sample (SRS) from each group.

Cluster sampling

Assigning each member of the population to a group (cluster) and selecting clusters using SRS for surveying.

Difference between cluster sampling and stratified sampling

In stratified sampling, subjects are chosen from each group, while in cluster sampling, subjects are only selected from sampled clusters.

Multistage sampling

Selecting a sample using a combination of different sampling methods.

Systematic random sampling

Selecting every kth subject from a list of the population after choosing the first sample element randomly.

Experimental Unit or Subject

Individuals on whom the experiment is conducted.

Factor

The explanatory variables in a study.

Treatment

The condition applied to the subjects in an experiment.

Control

Steps taken to minimize the effects of variables other than the independent and dependent variables.

Control group

A group that does not receive any treatment in an experiment.

Placebo

A fake treatment given to subjects in an experiment.

Blinding

Keeping subjects unaware of whether they receive the treatment or placebo.

Randomization

Using chance methods to assign subjects to treatments in an experiment.

Replication

Assigning each treatment to multiple experimental subjects to ensure reliability.

Bias

Systematically favoring one outcome over another in a study.

Completely randomized design

Randomly assigning subjects to different treatments in an experiment.

Randomized block design

Dividing subjects into blocks and then randomly assigning them to treatments within each block to reduce variability.

Matched pairs design

Pairing subjects based on a blocking variable and randomly assigning treatments within each pair.