Control of extraneous variables

Question 1

What will happen if extraneous variables are not controlled ?

Answer 1

Results will be skewed
Meaning they will not be valid
meaning they can not be applied or generalised as they may be incorrect.

Question 2

Demand characteristics

Answer 2

Reduce ecological validity
Ppts behave in certain ways for the study - may not behave the same outside of it.

If they geuss the purpose of the experiment may try to act in the ‘right’ way.
Can also rebel against the study - give wrong answers.

Question 3

How can you control demand characteristics ?

Answer 3

Single-blind methods
Drug trials can give half the ppts the real drug and the other half a placebo

Not tell the ppts which they have been given.

Equal - any differences can be down to the drug

Question 4

Investigator effects

Answer 4

Researchers behaviour affecting the ppts behaviour
Age - Gender - facial expressions

Interviews about sex - females may be uncomfortable speaking with a male and give different answers. (Invalid)

Question 5

How can you control investigator effects

Answer 5

Double-blind methods
Drug trial
Ppts/researcher both dont know which has been given.

Researcher cannot give any clues (consciously/unconsciously)

Question 6

Participant variables - how can it be controlled ?
Random allocation

Answer 6

Differences between ppts
Controlled by Random allocation

Extraneous variable = Gender
Experiment on effect of caffeine reaction times
If put into 2 groups - caffeine group/placebo group - one to men and one to women.
Lead to skewed results - men/women may act differently.

If R.A variables are evenly distributed between each group so results not skewed for one group more than the other.

Question 7

Situational variables

Answer 7

The environment that the experiment is conducted in

Question 8

How can situational variables being controlled ?

Answer 8

Standardisation
Keeping other variables the same

Test caffeine on reaction time
Study in - same room/time/equipment (all extraneous variables)

Question 9

Task order

Answer 9

Order in which tasks are completed

Question 10

How can task order be controlled ?

Answer 10

Counterbalancing to control the order in which tasks are completed
Group 1 - Do task A and then B
Group 2 - Do task B and then A