Extraneous and confounding variables

Question 1

Extraneous variable

Answer 1

Any variable, other than the independant variable, that may affect the dependant variable if it is not controlled. They are essentially nuisance variables that do not vary systematically with the independant variables.

Question 2

Confounding variable

Answer 2

A type of extraneous variable which varies systematically with the independant variable. Therefore investigators cannot tell if change in the dependant variable is caused be the independant variable or the confounding variable.

Question 3

Demand characteristics

Answer 3

If the researcher or the research situation is interpreted by participants as revealing the purpose of an investigation, the participant may change their behaviour within the research situation.

Question 4

Investigator effects

Answer 4

Any effect of the investigator’s behaviour (conscious or unconscious) on the research outcome (the dependant variable). This may include the design of the study and the selection of, and interaction with, participants during the research.

Question 5

Randomisation

Answer 5

The use of chance methods when allocating participants, designing materials and deciding the order of experimental conditions. This controls the effects of bias and participant variables.

Question 6

Standardisation

Answer 6

Using exactly the same formalised procedures and instructions for all participants in a research study to avoid investigator effects caused by different procedures/ instructions.

Question 7

Single-blind design

Answer 7

Any information that might create expectations is not revealed to the participants until the end of the study to control demand characteristics. Therefore participants may not be told the aim of the research or other details such as which condition of the experiment they are in or whether there is another condition at all.

Question 8

Double-blind design

Answer 8

Neither the participants nor the researcher who conducts the study (often a third party) are aware of the aims of the investigation. These are often used in drug trials so no investigator effects can influence participant behaviour.

Question 9

Social desirability bias

Answer 9

A tendency for respondents to answer questions in such a way that presents themselves in better light.

Question 10

Experimental realism

Answer 10

If the researcher makes the task sufficiently engaging the participant pays attention to the task and not the fact that they are being observed. Controls Demand characteristics