Lecturer: Dr. Adote Anum , Dept. of Psychology Contact Information: - - PowerPoint PPT Presentation

College of Education School of Continuing and Distance Education

2014/2015 – 2016/2017

Lecturer: Dr. Adote Anum, Dept. of Psychology Contact Information: aanum@ug.edu.gh

Session Overview

• Experimental psychology is that branch of psychology in which a

researcher manipulates an independent variable and observes the effects of the independent variable on a dependent variable.

• In an experiment, an independent variable (the cause) is

manipulated and the dependent variable (the effect) is measured; any extraneous variables are controlled. It is the manipulation of the independent variable and the control of extraneous variable that makes experimental method the most powerful method in research.

• In this Session, we will discuss the advantages and limitations of this

method and then describe the types of experimental methods and some designs.

Session Outline

The key topics to be covered in the session are as follows:

• Topic One: What is Experimental Research?
• Topic Two: Between-group and Within-group Experimental

Research Designs

• Topic Three:

Reading List

• Cozby, P. C. (2004). Methods in behavioral research (8th Ed.).

Mayfield Pub. Co. CA. (Chapter 2)

• http://open.lib.umn.edu/psychologyresearchmethods/

(Chapter 6, pages 100 – 122). Please refer to Sakai for the PDF version of this textbook.

WHAT IS A EXPERIMENTAL RESEARCH?

Topic One

Experimental Research

• What is Experimental Research?

– is a systematic and scientific approach to research in which the researcher manipulates one or more variables, and controls and measures any change in other variables.

Basics of an Experiment

• Use of a Control group

– This is a condition that receives no treatment so that they are compared to the treatment group on the DV

• Randomisation (random assignment)

– Subjects should be randomly assigned to either control or treatment group

Basics of an Experiment

• Order Effects

– Refers to the Effects that occur as a result of the serial position in which the condition or treatment occurs.

• Carry-Over effects

– an effect that "carries over" from one experimental condition to another

Basics of an Experiment

• Counterbalancing

– Used to control order effects – Subject group receive the treatment in alternative order – Can be complicated when there are more than 2 conditions

First Second Third Order 1 A B C Order 2 B C A Order 3 C A B

Types of an Experiment

• Laboratory/Controlled Experiments

– This type of experiment is conducted in a well-controlled environment – not necessarily a laboratory – and therefore accurate measurements are possible. – Strengths

• It is easier to replicate (i.e. copy) a laboratory experiment. This is because a standardized

procedure is used.

• They allow for precise control of extraneous and independent variables. This allows a

cause and effect relationship to be established.

– Limitation

• Limitation: The artificiality of the setting may produce unnatural behavior that does not reflect real

life, i.e. low ecological validity. This means it would not be possible to generalize the findings to a real life setting.

– Limitation: Demand characteristics or experimenter effects may bias the results and become confounding variables.

Types of an Experiment

• Laboratory/Controlled Experiments

– Limitations

– The artificiality of the setting may produce unnatural behavior that does not reflect real life, i.e. low ecological validity. This means it would not be possible to generalize the findings to a real life setting. – Demand or experimenter effects may bias the results become confounding variables.

Types of an Experiment

• Field Experiments
• Field experiments are done in the everyday (i.e. real life)

environment of the participants. The experimenter still manipulates the independent variable, but in a real-life setting (so cannot really control extraneous variables).

• Strength:

– Behavior in a field experiment is more likely to reflect real life because of its natural setting, i.e. higher ecological validity than a lab experiment. – There is less likelihood of demand characteristics affecting the results, as participants may not know they are being studied. This occurs when the study is covert.

Types of an Experiment

• Field Experiments

– Limitation: There is less control over extraneous variables that might bias the results. This makes it difficult for another researcher to replicate the study in exactly the same way.

BETWEEN-GROUP & WITHIN-GROUP EXPERIMENTAL RESEARCH DESIGNS

Topic Two

Between-Groups Design

• Between-groups design is used to assess the

effect of different levels of an independent variable by administering each level to a different group of subjects and then comparing the performance of the group on the dependent variable.

• The simplest between-groups designs

include a single independent variable with two levels. When using the design, the study includes two groups that each receives a different level of the IV.

Characteristics of Between-Groups Design

• Another feature of a between-subjects design is that

it allows only one score per participant (every score represents a separate, unique participant)

• A between-subjects experimental design requires a

separate, independent group of individuals for each treatment condition compared

Characteristics of between-Groups design

• Individuals are assigned to groups using a procedure

that attempts to create equivalent groups

• The general goal of between-subjects experiment is

to determine whether differences exist between two

• r more treatment conditions

Between-Group Designs

• Advantages
• Carry-over effects that occur because of practice/fatigue
• contrast effects that result from comparing one treatment to

another (e.g. room temperature)

• Avoids effects of maturation
• contrast effects that result from comparing one treatment to

another (e.g. room temperature)

• Time saving

Disadvantages of Between-Subjects Designs Disadvantages

– large number of participants (problem with special populations) – Not practical for some types of studies – Inability to maintain homogeneity across groups – Assignment bias

Between- and Within-Subject Design

• Within-Subject Design
• There is one experimental/treatment group
• No control group
• The Experimental/Treatment act as its own

control

• Order and Sequencing can be controlled if each

subject receives each condition

References

• Cozby, P. C. (2004). Methods in behavioral research

(8th Ed.). Mayfield Pub. Co. CA. (Chapter 2)

• http://open.lib.umn.edu/psychologyresearchmeth
• ds/ (Chapter 6, pages 100 – 122). Please refer to

Sakai for the PDF version of this textbook.

THANK YOU