# Lecture Slides

Week 6 Lecture Slides

# Concepts

Classical Experimental design

Independent variable

Dependent variable

Random assignment

Pretest

Posttest

Experimental group

Control group

Key Concepts:

Double-blind experiment

Confederates

Placebo

Deception

Debrief

Types of experiments:

Classical experimental design

True experiment

Quasi-experiment

One-shot case study

Natural experiment

Field experiment

Validity:

Internal validity

External validity

Variable:

Conceptual

Operational

# Random Assignment

Random assignment = Using a mathematically random process to sort participants into two or more groups.

E.g. Flip a coin to assign to groups

Matching cases = An alternative to random assignment, where for every participant in experimental group, another participant is found for control group with almost identical characteristics

E.g. Create two groups of countries: one with minimum wage, one without. Use matching to make sure each case is matched with a case with similar GDP per capita.

# The classical experimental design

The classical experimental design includes:

1. Independent variable = treatment (cause)
2. Dependent variable = outcome (effect)
3. Pretest = A measurement of the dependent variable before introducing the independent variable
4. Posttest = A measurement of the dependent variable after introducing the independent variable
5. Experimental group = a group that receives the independent variable (or receives a higher level of it)
6. Control group = a group that does not receive the independent variable (or receives a lower level of it)
7. Random assignment = mathematically random assignment to control or experimental group.

# Exercise: Identify the following elements of a classical experimental design in Migram’s Authority experiment?

Watch the following video, which is a recreation of the famous experiment by Stanley Milgram on obedience to authority.

Identify the following elements of a classical experimental design in Migram’s Authority experiment?

• independent variable
• dependent variable
• pretest
• post test
• experimental group
• control group
• random assignment

Video of recreation of Migram’s obedience experiment

Last updated on 13 April, 2020 by Dr Nicholas Harrigan (nicholas.harrigan@mq.edu.au)