Key concepts

There are two basic types of research design:

• True experiments
• Quasi-experiments

The purpose of both is to examine the cause of certain phenomena.

True experiments, in which all the important factors that might affect the phenomena of interest are completely controlled, are the preferred design. Often, however, it is not possible or practical to control all the key factors, so it becomes necessary to implement a quasi-experimental research design.

True experimental design is regarded as the most accurate form of experimental research, in that it tries to prove or disprove a hypothesis mathematically, with statistical analysis.

True experimental design is regarded as the most accurate form of experimental research, in that it tries to prove or disprove a hypothesis mathematically, with statistical analysis.

True experimental design is regarded as the most accurate form of experimental research, in that it tries to prove or disprove a hypothesis mathematically, with statistical analysis.

True experimental design is regarded as the most accurate form of experimental research, in that it tries to prove or disprove a hypothesis mathematically, with statistical analysis.

A true experiment is a type of experimental design and is thought to be the most accurate type of experimental research. This is because true experiments support or refute a hypothesis using statistical analysis. A true experiment is also thought to be the only experimental design that can establish cause and effect relationships. So what makes a true experiment?

There are three criteria that must be met in a true experiment

1. Control group and experimental group
2. Researcher-manipulated variable
3. Random assignment

True experimental design is regarded as the most accurate form of experimental research, in that it tries to prove or disprove a hypothesis mathematically, with statistical analysis.

For an experiment to be classed as a true experimental design, it must fit all of the following criteria.

• The sample groups must be assigned randomly.
• There must be a viable control group.
• Only one variable can be manipulated and tested. It is possible to test more than one, but such experiments and their statistical analysis tend to be cumbersome and difficult.
• The tested subjects must be randomly assigned to either control or experimental groups.

Pre-experiments are the simplest form of research design. In a pre-experiment either a single group or multiple groups are observed subsequent to some agent or treatment presumed to cause change.

Types of Pre-experimental design:

• One-shot case study design
• One-group pretest-posttest design
• Static-group comparison

One-shot case study design

A single group is studied at a single point in time after some treatment that is presumed to have caused change. The carefully studied single instance is compared to general expectations of what the case would have looked like had the treatment not occurred and to other events casually observed. No control or comparison group is employed.

One-group pretest-posttest design

A single case is observed at two time points, one before the treatment and one after the treatment. Changes in the outcome of interest are presumed to be the result of the intervention or treatment. No control or comparison group is employed.

Static-group comparison

A group that has experienced some treatment is compared with one that has not. Observed differences between the two groups are assumed to be a result of the treatment.

True experimental design is an integral part of science, usually acting as a final test of a hypothesis. Whilst they can be cumbersome and expensive to set up, literature reviews, qualitative research and descriptive research can serve as a good precursor to generate a testable hypothesis, saving time and money. Whilst they can be a little artificial and restrictive, they are the only type of research that is accepted by all disciplines as statistically provable.

For an experiment to be classed as a true experimental design, it must fit all of the following criteria.

• The sample groups must be assigned randomly.
• There must be a viable control group.
• Only one variable can be manipulated and tested. It is possible to test more than one, but such experiments and their statistical analysis tend to be cumbersome and difficult.
• The tested subjects must be randomly assigned to either control or experimental groups.