L8 - Control of Extraneous Variables

Question 1

What are participant variables?

Answer 1

• These are characteristics of the participants which may affect the DV (ie age, gender, personality)
• Matched pairs and repeated measures help avoid participant variables.
• However, repeated measures can lead to order effects, so counterbalancing should be used to avoid this.

Question 2

What is random allocation?

Answer 2

• It involves all the participants being identified either by name or number.
• The names/numbers are put in a hat.
• Then, assign alternate names/numbers drawn to condition 1 then condition 2 and so on until both conditions are full.

Question 3

What are environmental variables?

Answer 3

• These are factors in the environment where the experiment is conducted, that could affect the DV.
• e.g. temp, time of day, lighting)
• To fix this, standardisation is used, which is making sure that all conditions, materials and instructions are the same for all participants.

Question 4

What are investigator effects?

Answer 4

• This is when the person collecting try data has knowledge of what the research aim is.
• Observer bias is a type of investigator effect.
• The double blind technique works to prevent this happening. This is when neither the participant or the observer know the hypothesis of the study, ie the aim.

Question 5

How can demand characteristics be prevented?

Answer 5

By using the single blind technique. This involves making sure participants do not know what the hypothesis is or what condition they’re in.

However, this is difficult to accomplish when using as repeated measures design.