Experimental Design Concepts

Experimental Design

• A confounding variable occurs when an experimenter cannot distinguish between the effects of different factors on a variable.

Placebo Effect and Blinding

• The placebo effect: a subject reacts favorably to a placebo when no medicated treatment has been given.
• Blinding: a technique that makes subjects unaware of the treatment (or placebo) they receive.

Types of Experiments

• Double-blind experiment: neither the experimenter nor the subjects know which treatment is being given.

Randomization Techniques

• Completely randomized design: assigns subjects to different treatment groups through random assignment.
• Randomized block design: ensures subjects with certain characteristics are assigned to each treatment.

Design Examples

• Randomized block design example: split subjects into groups according to gender or age, then randomly assign each group to different treatments.

Matched Pairs Design

• Pairs up subjects according to similarities.
• One subject in the pair receives one treatment, while the other receives a different treatment.

Experimental Basics

• Sample size: the number of participants in the experiment.