Control of Variables

Question 1

What are extraneous variables?

Answer 1

They are any other variable that (other than the IV) that can have an effect on the DV if not controlled.

Question 2

What is a confounding variable?

Answer 2

They vary systematically with the IV. They usually only affect one condition of the experiment and it becomes a second, unwanted IV.

Results are meaningless as we do not know if the changes in the DV were due to the confounding variable or manipulation of the IV.

Question 3

How does random allocation work?

Answer 3

It’s a way of overcoming participant variables.

1. Assign each participant a number.
2. Write numbers on a slip of paper, fold and place into a hat.
3. The first number drawn goes into condition A, the next number drawn goes into condition B and repeat until all participants have been assigned a condition.

Question 4

How do you write standardised instructions?

Answer 4

Used by researchers so participants understand fully what they must do during the study. This avoids researcher bias.

MUST BE WRITTEN AS A SCRIPT:
• Must give a step by step account of everything the participants must do from beginning to end.
• Task that participants have to do is made completely clear
• Include timings if possible so participants know how much time they have available
• ask if there are any further questions before they start

Question 5

What is counter balancing?

Answer 5

A method of balancing out order effects and is used in a repeated measure design.

1. Split participants into two groups.
2. One group does condition A then B
3. The second group does condition B then condition A