Control in repeated measures

Question 1

Order effects

Answer 1

Only likely in repeated measures designs as the same participants are used in each condition

Occur when participants experience practice (learning effect) or tiredness (fatigue effect)

Which can affect their performance in the second condition, making the results invalid

Question 2

Overcoming order effects 1

Answer 2

Counterbalancing

Strategy to overcome which involves participants being divided into 2 groups

First group experiences condition A followed by condition B

2nd group experience the conditions in reverse order: condition B followed by condition A

Order effects not removed but balanced between the 2 conditions

Question 3

Overcoming order effects 2

Answer 3

Randomisation

Participants are randomly assigned to experience:

Condition A followed by condition B or,
Condition B followed by condition A

Can occur by flipping a coin or drawing names from a hat

Order effects not removed but balanced between 2 conditions

Question 4

Control

Answer 4

Achieved when all variables (other than IV) are held constant

In particular, psychologists should control against:

Extraneous variables - uncontrolled variables that could affect the DV in a random way

Confounding variables - uncontrolled variables that could affect the DV in a systematic way

Question 5

Control achieved through 1

Answer 5

Random allocations of participants

When participants are randomly allocated, groups are likely to be unbiased as everyone has an equal chance of being allocated to each condition

E.g. it ensures that one group is not more intelligent than the other by giving everyone an equal chance of appearing in each condition

Question 6

Control is achieved through 2

Answer 6

Standardisation

Means that all participants have the same experience, so that any variation in the DV is not caused by variation between participants or conditions

1 key way to achieve standardisation is by using standardised instructions, which allow the experimenter to behave in the same way with all participants

Question 7

Demand characteristics

Answer 7

When the participants perceive the demands of the study and act accordingly, lowering internal validity of research due to a change in their natural behaviour

E.g. may guess demands of study and act positively, trying to please experimenter with ‘right’ answer

Question 8

Minimising demand characteristics

Answer 8

Single blind technique

Where participants don’t know which condition they have been allocated to

They are then less likely to perceive the demands of the experiment (and cannot act in a particular way as a result)

Question 9

Experimenter effects

Answer 9

Occur when some characteristic of the experimenter causes participants to behave unnaturally, lowering internal validity

E.g. participants may find the experimenter attractive or may take a dislike to them, causing them to behave differently

Question 10

Minimising experimenter effects

Answer 10

Double-blind

When both the participants and experimenter don’t know the aims or conditions of the research

Researchers are then unable to influence the participants in any way

Person carrying out experiment will have some information about the procedure, but the amount of information given to them can be minimised by the psychologist leading the research

Question 11

Pilot study

Answer 11

To check level of control in procedures, a small-scale pilot study can be run before carrying out the actual experiment

Can be used to check if the design works; if participants can easily understand the instructions; and if there are any sources of bias that require control

Participants can also provide their feedback about the instructions or any aspect of the procedure, so that changes can be made

In this way, it is possible to overcome these issues before the experiment takes place, increasing internal validity of research, saving time and money