11.Types Of Extraneous Variables & Their Controls

What are the different types of extraneous variables?

• Participant variables

• Situational variables

• Demand characteristics

• Experimenter effects

• Placebo effects

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Participant variables

Personal characteristics of an individual participants , potentially influencing their responses.

• can be Biological, Psychological, Social

How do you control participant variables

• ensure that there is a uniform spread of participant characteristics between conditions through random sampling

• using appropriate experimental design

Situational variables

External factors other than IV associated with the experimental setting that may influence participant response and result.

• background noise

• time of day

• temperature

How to control situational variables

to ensure that all situational variables are present in all conditions so the variables can cancel out.

Demand characteristics

Cues in an experiment that may influence or bias a participant's response, suggesting what kind of response the experimenter expects.

Experimenter effects

Any influence the experimenter may have on the results of their investigation, including their interaction with participants and biases.

Placebo effect

Change in participants' behavior due to belief that they are receiving some kind of experimental treatment, rather than the effects of the independent variable.

How can a placebo effect be minimised

• Control group can be given Placebo which is a Fake or inactive treatment that substitutes for a real substance

Control

The aim to ensure that participant characteristics and situational variables are accounted for, minimizing their influence on the dependent variable.

Order effects

Effects that can arise in within subjects designs when the sequence of tasks influences performance on the dependent variable. (one task affects performance of the next)

Practice effects

• when repeating tasks can improve or impair performance

Counterbalancing

A method to control order effects by altering the sequence of treatments or tasks for participants in a balanced way.

What are demand characteristics

• cues in a experiment that influence/bias participant response

• can be produced by experimenter or setting

  eg/ Participants guessing hypothesis & attempting to act in ways they think will support hypothesis

How can you control demand characteristics

Blind procedures, Deception, Experimental design

Why is deception used to prevent demand characteristics?

• used if potential benefits outweighs harms

• no other viable options

• ensure participants respond naturally though concealing purpose of experiment.

Single blind procedure

A method where participants are unaware of which experimental condition they are in to reduce bias.

Double blind procedure

A method where both participants and experimenters are unaware of the conditions participants are assigned to, preventing bias from both sides. only a researcher removed from the experiment knows who is in what condition

Experimented expectancy

• involves cues experimenter provides about responses participants should make in experiment , which can produce a self-fulfilling prophecy.

• Also involves unintentional errors or biases in treatment of data when analysing results (unconscious mistakes)

What is Experimenter effect

refers any influence experimenter may have on the results of their investigation

• unintentional errors when making observations, measuring responses, analysing or interpreting results