RM: Types of experimental design Flashcards
(13 cards)
What is Repeated measures design?
All participants receive all levels of the IV.
e. g.
* Each participant does the task with the TV on- e.g. does a memory test.*
* Then perhaps a week later, each participant does a similar test without the TV on.*
We compare the performance (DV) of the participant on the two tests.
What are the limitations of Repeated measures design?
- The order of conditions may affect performance ( an order effect) e.g. they may do better on second test due to a practise effort or being less anxious.
- Boredom effect- may do worse due to being bored.
- When participants do the second test- they may guess the purpose of the experiment, which may affect their behaviour.
What is the method of dealing with limitations for Repeated measures design?
- Researchers may use two different tests to reduce a practise effect- though the two tests must be equivalent!
- Use counterbalancing- in order to avoid participants guessing the aims of a study, a cover story can be presented about the purpose of the test.
What is a Independent groups design?
Participants are placed in seperate (independent) groups. each group does one level of the IV.
e.g.
- Group A does the task with the TV on (one level of the IV)
- Group B does the task with no TV ( the other level of the IV)
We compare the performance of the two groups!
What are the limitations of Independent groups design?
- The researcher cannot control the effects of participants variable.
- Independent groups design needs more participants than repeated measures design in order to end up with the same amount of data.
How do you deal with the limitations of independent groups design?
Randomly allocate participants to conditions which (theoretically) distribute participant variables evenly.
Random allocation can be done by putting the participant names in a hate and drawing out the names so that every other person goes in Group A.
What is matched pairs design?
- Use to groups of participants but match participants on key chacarturistics believed to affect performance.
- One member of the pair is allocated to group A and the other member to group B- the procedure is then the same for independent groups!
- The characteristics for matching must be relevant to the study!!!
What are the limitations of matched pairs design?
- Very time consuming and difficult to match participants on key variables! (Researcher- may have to start with a large group of participants to ensure they can obtain matched pairs on key variables!)
- Its not possible to control all participant variables- you can only match variables known to be relevant- but it may be others that are important!
How do you deal with the limitations for the matched pair design?
- Restrict the number of variables to match on to make it easier!
- Conduct a pilot study (small versions of proposed studies to test their effectiveness and make improvements) to consider key variables that might be important when matching!
What does counterbalancing ensure?
Ensures that each condition in a repeated measures design is tested first or second hand in equal amounts
What are the two conditions to counterbalance order effects?
Condition A- test done in the morning.
Condition B- test done in the afternoon.
COUNTERBALANCING
Way 1. AB or BA ?
Divide participants into two groups:
- Group 1: each participant does A then B.
- Group 2: each participant does B then A
(this is still a repeated measures design)
COUNTERBALANCING
Way 2. ABBA?
This time, all participants take part in each condition twice.
- Trial 1: Condition A (morning)
- Trial 2: Condition B (afternoon)
- Trial 3: Condition B ( afternoon)
- Trial 4: Condition A ( morning)
Then we compare scores on 1 & 4 with trials 2 & 3. ( This is still a repeated measures design as we are comparing the scores of the same person.)
