Control Of Extraneous Variables

Question 1

Extraneous variables and validity

Answer 1

In order to ensure that a study has validity, extraneous variables must be controlled for to prevent from becoming confounding variables

Question 2

What are participant variables?

Answer 2

• characteristics of the participant which may affect the DV (e,g, intelligence, gender, age, personality etc..)
• matched pairs + repeated measures can help to avoid participant variables
• however, repeated measures can lead to order effects so counterbalancing should be used to avoid this
• random allocation of parts to conditions (e.g. drawing names out of a hat) when using independent groups should also ensure groups are not biased
• random allocation is not possible for a quasi-experiment

Question 3

Describe the process of random allocation

Answer 3

• names in a hat and draw them out for whoever large sample is
• all participants being identified by name or a number = out into a hat or into a computer
• assign alternate names/ numbers drawn to condition 1 then condition 2 and so on until there are required number in each condition

Question 4

What are environmental variables ?

Answer 4

• factors in the environments where the experiment is conducted that could affect the DV (e.g. temperature, time of day, lighting, noise etc..)
• use standardisation (make sure that all conditions, materials and instructions are the same for all participants)

Question 5

What are investigator effects?

Answer 5

When the person collecting the data has knowledge of what the research aim is is and that knowledge affects the data obtained

Investigator effects can be overcome by the double blind technique = neither the parts or the investigator know the hypothesis of the study or what condition the participant is in

Certain physical characteristics e.g. a gem gender + ethnicity etc.. of the investigator may inadvertently influence the results of their research

Standardised scripts should be written to ensure that the investigator acts in a similar way with all participants + should also be trained to greet all parts the same way + ask q’s in a neutral tone

Question 6

What are demand characteristics?

Answer 6

A type of extraneous variable:

• there are many features of research studies that may enable participants to guess a study’s purpose and what is expected of them
• can lead to the participant trying to:
• please the researcher by giving the ‘right’ results
• trying to annoy the researcher by giving the wrong results (the screw-you-effect)
  acting unnaturally out of nervousness
• acting unnaturally out of social desirability bias
• Observer effects and interviewer effects are types of demand characteristics

Question 7

How can demand characteristics be overcome?

Answer 7

Can be overcome w/ single blind technique = make sure parts dk hypothesis or condition they’re in

More difficult to accomplish when using repeated measures design