EXPERIMENTAL DESIGN Flashcards
What is an experimental design?
Experimental design refers to the way in which participants are used in experiments (i.e. how the testing of participants is arranged in relation to the different experimental conditions).
How many types of experimental design have been identified by psychologists?
Three types of experimental design have been identified by psychologists.
What are the three types of experimental design within psychology?
- Independent groups
- Repeated measures
- Matched pairs
What is an independent groups design?
An independent groups design is when two separate groups of participants experience two different conditions of the experiment. If there are two levels of the IV this means that all participants experience one level of the IV only. The performance of the two groups would then be compared.
How could an independent groups design be applied to the energy drink investigation?
One group of participants (group 1) drinking the energy drink (condition A, the experimental condition)
A different group of participants (group 2) drinking the water (condition B, the control condition)
How would the two independent groups be compared in the energy drink experiment?
In the energy drink experiment we would compare the difference in the mean number of words spoken in the five-minute period after drinking for each group.
What is a repeated measures design?
A repeated measures design requires all participants to experience both conditions of the experiment. Following this, the two sets of data from both conditions would be compared to see if there was a difference.
How could a repeated measures design be applied to the energy drink investigation?
-Each participant would first experience condition A
(the experimental condition)
-Each participant would then later be tested again in condition B (the control condition)
How does a repeated measures design differ from an independent groups design?
A repeated measures design guarantees that we are comparing ‘like with like’. In contrast, an independent groups design assesses the performance of two different groups of people, which is often viewed as a problem.
What is a matched-pairs design?
In a matched-pairs design, participants are paired together on a variable or variables relevant to the experiment. Then one participant from each pair would be allocated to a different condition of the experiment.
How could a matched-pairs design be applied to a study investigating memory?
In a memory study participants might be matched on their IQ, as this might be a good indicator of their ability to recall information. The two participants with the first and second highest IQ scores would be paired together, as would the participants with the third and fourth highest, and so on. Then one participant from each pair would be allocated to a different condition of the experiment.
Which variable does a matched-pairs design attempt to control?
A matched paired design attempts to control for the confounding variable of participant variables.
What is required for a matched-pairs design to be effective?
A matched-pairs design often necessitates the use of a pre-test if matching is to be effective.
How might the participants be matched effectively in the SpeedUpp experiment
In the SpeedUpp study a psychologist might observe participants interacting in a room before the experiment begins and select the two people that appear to be the chattiest. One of the pair would be placed in condition A and the other in condition B.
What is random allocation?
To address the problem of participant variables in an independent groups design, participants should be randomly allocated to the different experimental conditions. Random allocation attempts to evenly distribute participant characteristics across the conditions of the experiment using random techniques (e.g. pieces of paper with A or B written on them are placed in a hat and the researcher selects them one at a time to assign participants to groups).
