Lesson 8 - Control of Extraneous Variables

Question 1

Extraneous Variables

Answer 1

In order to ensure that a study has validity, extraneous variables must be controlled to prevent them from becoming confounding variables

Question 2

Participant Variables (PV)

Answer 2

Characteristics of participants that may affect DV
Choosing appropriate experimental design can help overcome these extraneous variables
Matched pairs and repeated measures prevent PVs but repeated measures can lead to order effects so use of counterbalancing needed
Random allocation for independent groups ensures no bias however random allocation not possible for quasi-experiments

Question 3

Environmental Variables

Answer 3

Factors in environment where experiment is conducted that could affect DV
Answer to this is standardisation

Question 4

Investigator Effects

Answer 4

Person collecting data has knowledge of what the research aim is and that knowledge affects data obtained
Observer bias is an example
Can be overcome by double blind technique when neither participant nor investigator know hypothesis of study or condition the participant is in

Question 5

Demand Characteristics

Answer 5

Many features of research studies that may enable participants to guess a study’s purpose and what is expect of them
Can lead to the participant trying to please the researcher by giving the “right” results, try to annoy the research by giving wrong results (screw-you-effect), acting unnaturally out of nervousness or acting unnaturally our of social desirability bias
Observer effects and interviews effects are types of demand characters
Can be overcome with single blind technique