Control of extraneous variables

Question 1

why must variables in an experiment be controlled?

Answer 1

essential in producing reliable results – where the IV is certain to have caused the difference in the DV.

Question 2

when a variable is unexpected and not controlled what is this called?

Answer 2

an extraneous variable, (unwanted) or confounding variables.

Question 3

extraneous variables can be caused by two types of errors what are they?

Answer 3

random error or constant error

Question 4

random errors can’t be predicted list two things that can cause a random error.

Answer 4

• Participant characteristics e.g. state of mind and level of motivation.
• Environmental factors that can be a distraction e.g. incidental noise and room temperature.

Question 5

Constant errors affect the dependent variable in a consistent way list two things that can cause a constant error.

Answer 5

• a failure to counterbalance or randomize the presentation order of experimental conditions
• participant differences in independent groups designs
• Errors of measurement that affect one condition more than another.

Question 6

how can constant errors be prevented?

Answer 6

sources of error should be eliminated by good experimental design.