Experimental Design

When all relevant variables are controlled so that the observed changes in the dependant variable must be due to changes in the independant variable.

An additional experiment designed to eliminate alternative explanations for the main experiment. This shows that the observed changes in the dependant variable are due to changes in the independant variable. 

A group or sample treated in exactly the same way as the experimental group, except for the factor being investigated. this ensures that the change in the dependant variable is caused by the independant variable changing.

A dummy pill, injection or treatment that has no physiological effect; this ensures that the independant variable is causing the changes in the dependant variable. 

Randomised Controlled Trial. The best experimental design.

Randomised: The study and the control groups are randomly selected. This will prevent bias.

Placebo-controlled: The study group is compared to a control group.

Double-Blind: Neither the subjects or the investigators know who is in the experimental or control groups. 

A method or technique that has been shown to produce valid and reliable results.

A suggested explanation of observations or results that can be tested. also, known as a scientific hypothesis.