Experimental designs Flashcards
(14 cards)
What does experimental designs refer to?
Experimental design refers to the way in which participants are used in experiments - how they are arranged in relation to the different experimental conditions
What is a pilot study?
A small-scale prototype of a study that are carried out in advance of the full research to find out if there are any problems with the following:
1. Experimental design
2. Instructions for participants
3. Measuring instruments
Pilot studies are carried out to ensure time, money and effort are not wasted
It’s important that a pilot study uses a sample that (although smaller) is representative of the target population that will be used in the main research
What is an independent group design?
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
Give an example of a independent group design using red bull
- One group will drink the energy drink - experimental condition
- One group will drink the water - control condition
The performance of the two groups would then be compared
In the Red Bull experiment we would compare the difference in the mean number of words spoken in the 5 minutue period after drinking for each group/ condition (Red Bull or water)
Give 2 strengths of an independent group
- Avoids order effect partic - As participants only take part in one condition, they are less likely to become bored and give up
- Reduces demand characteristics - Participants are only taking part in one condition so they are less likely to guess the aim of the experiment and display demand characteristics making the results higher in v
Give 2 limitations of an independent group
- More participants are needed as different people take part in the different conditions - Makes it more expensive and time-consuming
- Participant variable may affect the results - EG: different ages, sex or social background may affect the results by acting as an extraneous variable on the DV therefore the psychologists cannot be sure whether the IV casued the changes
What is a repeated measures design?
When all participants experience both conditions of the experiment
Red Bull example:
Each participant would experience condition A - drinking Red Bull
Each participant would then (later on) be tested again in condition B - water
Following this the two mean scores from both conditions would be compared to see if there was a difference
Give a strength of repeated measures
Fewer participants are needed - the design is less costly and time consuming
The use of the same participants across conditions also reduces the possibility of participant variables playing a part in the different results obtained - the effect on the DV can be attributed to the IV with more confidence
Give a weakness of repeated measures
As the same participants take part in both conditions of the experiment, order effect can occur
Participants who experience practice effects may perform better in the second condition as they know what is expected of them
Participants who experience fatigue/ boredom may perform worse in the second condition
Researchers can use counterbalancing which helps to reduce order effects - Half the participants take part in ‘condition A’ and then ‘condition B’ while the other half do ‘condition B’ and then ‘condition A’
Repeated measure designs are more prone to demand characteristics as the participants are more likely to guess the aim of the experiment
What is a matched pairs design?
Participants are paired together on a variable or variables relevant to the experiment
Example:
In a memory study participants may be matched on their IQ
The two highest scoring participants would be paired together
Then each participant from their pair would be allocated a different condition
This controls the confounding variable of participant variables
Pre-testing is usually required to ensure matching is effective
Give the strengths of matched pairs
Participant variables are reduced as researchers pair up people with similar abilities or characteristics
Order effects (practice or fatigue) are less of an issue as participants only take part in one condition
Give weaknesses of matched pairs
More participants are needed making the design more expensive and time-consuming
It can be hard to find a close or exact match which means that individual differences may still play a role in the measurement of the DV
What is meant by random allocation?
To reduce the problem of participant variable in an independent group design, participants should be randomly allocated to different experimental conditions
Random allocation tries to evenly distribute participants characteristics across the conditions
This usually uses random techniques such as:
Writing A and B on a piece of paper, placing them in a hat and then getting the participants to select one, thus assigning them into their conditions group
What is counter balancing/ ABBA technique?
This is a technique used to attempt to control order effects in a repeated measures design - doesn’t remove or prevent it
In counterbalancing, half the participants take part in condition A then B, and the other half take part in condition B and then A
Participant 1: A then B
Participant 2: B then A
Participant 3: A then B etc
