Experimental designs Flashcards
What is an experimental design?
The different ways in which the testing of participants can be organised in relation to the experimental conditions
What are the three different types of experimental designs?
- Independent groups design
- Repeated measures design
- Matched groups design
What is an independent group design?
An independent group design is when two separate groups of participants experience two different conditions of the experiment. The performance of each group would then be compared.
What type of data do independent group designs produce?
Independent group designs produce unrelated data
What technique is used to avoid researcher bias?
Participants are randomly allocated to avoid researcher bias
What is a strength of using the independent groups experimental design? (order effects)
The strength of using an independent groups design are that order effects are not a problem whereas they are a problem for repeated measures designs. Participants are less likely to guess the aims
What is a limitation of using the independent groups experimental design? (cost)
Independent group designs are less economical than repeated measures as each participant contributes single result only. Twice as many participants would be needed to produce equivalent data to that collected in a repeated measures design.
What type of data is produced after the use of a repeated measures design?
Related data
What is a repeated measures design?
A repeated measures design involves all the participants completing all the conditions of the experiment
What is a strength of using a repeated measures experimental design? (participant No + group differences)
In repeated measures designs, less participants are needed to take part and more data is produced. Additionally, there are no group differences as the same participants are used in each condition
How many sets of data are produced, what is done with these sets of data?
Two sets of data are produced from the participants, then later both are compared
What is counterbalancing?
Counterbalancing is when half the participants take part in condition one then two and the other half of participants take part in condition 2 then 1
What is a limitation of using a repeated measures experimental design? (order of tasks)
The biggest issue for repeated measures is that each participant has to do at least two tasks and the order of these tasks may be significant, to deal with this researchers use counterbalancing. Counterbalancing - half the participants take part in condition A then B and the other half take part in condition B then A.
What is a matched pairs design?
A matched pairs experimental design has participants only take part in a single condition
What type of data is produced?
Related data
How are participants assessed and matched?
Participants are assessed and matched based on characteristics relevant to the study
What type of humans are usually the best match?
Often identical twins (monozygotic) are used due to perfect match
What is a strength of using a matched pairs experimental design? (order effects and demand characteristics)
Participants only take part in a single condition so order effects and demand characteristics are less of a problem. Demand characteristics are significantly less likely, since participants are less likely to guess the purpose of the study.
What is a limitation of using a matched pairs experimental design?
Matched pairs design can be time consuming and expensive, particularly if a pre test is required, so this a less economical than other designs. Additionally, matching can be difficult and often it is impossible to match all characteristics especially when unmatched characteristics are important to study
Identify what experimental design has been used:
2. A psychologist is investigating the effect of music on concentration. A group of participants are given a series of crossword puzzles to solve, first in a silent room, then when a classical music is played, and then when rock music is played. The time taken to solve each puzzle is recorded
An repeated measures design is used in this experiment
Identify what experimental design has been used:
1. A researcher is interested in whether alcohol has an effect on memory. One group of participants are given a list of words to learn and then given an alcoholic drink. The other group is given the same list of words, and a glass of water. The number of words they can remember is recorded
An independent group design is used in this experiment
Identify what experimental design has been used:
3. A scientist has developed a drug which he believes will increase IQ. He has two groups of participants; one group he gives the drug to, and other he gives a placebo to. After two weeks, he tests their IQ. To try and avoid an participant variables, he ensures that he has an equal number of men and women in each group, and that the participants are of similar ages, intelligence and social background
A matched pairs design is used in this experiment
Identify what experimental design has been used:
4. A psychologist wants to test the theory that doctors have better spatial awareness than teachers. A group of doctors and teachers are given a series of spatial awareness tasks (such as rotating a cube in their heads, giving directions on a map etc) which produces a spatial awareness score
An independent group design is used in this experiment
Identify what experimental design has been used:
5. It is proposed that people are more willing to give money to a male rather than a female charity collector. This is tested by showing participants photographs of male and female faces and a description of a fake charity that they represent. The participants are then asked to say how much (if any) money they would donate
An independent group design is used in this experiment
Identify what experimental design has been used:
6. A researcher is interested in the effect of marriage on general happiness in life. He measures the happiness of engaged people one year before their wedding, and then measures their happiness again one year after they have got married
An repeated measures design is used in this experiment
