control of extraneous variable

Question 1

order effects

and how can it be controlled

Answer 1

• Order effects can occur in a repeated measures design and refers to how the positioning of tasks influences the outcome e.g. practice effect or boredom effect on the second task.
• these can be controlled using counterbalancing (e.g. half the participants do condition A followed by B and the other half do B followed by A)

Question 2

participant variables

and how can this be reduced

Answer 2

participants in one group may differ in a significant way from participants in another group.

• This risk can be reduced via random allocation (participants randomly assigned to groups) or by matched pairs (see experimental designs).

Question 3

situational variables

and how can they be reduced

Answer 3

• factors in the environment that may affect the DV.
• These can be reduced by using a standard procedure (see experiments).

Question 4

investigator effects

and how can it be controlled

Answer 4

• occur when a researcher unintentionally, or unconsciously influences the outcome of any research they are conducting
• Can be controlled using double-blind control (participants are not told the true purpose of the research and the experimenter is also blind to at least some aspects of the research design)
• or standardized instructions and/or procedures (see lab experiments).

Question 5

demand characteristics

and how can it be reduced

Answer 5

• Occur when participants try to make sense of the research situation they are in and try to guess the purpose of the research or try to present themselves in a good way.
• Can be reduced using Double-blind control (see above) or Single-blind control (Participants are not told the true purpose of the research).