Research Methods: Experiments Flashcards
What are experimental designs?
The different ways in which participants can be organised in relation to experimental conditions.
What is an independent groups design? Give a limitation of it:
Participants are allocated to different groups where each group represents one experimental condition.
Limitation:
Participants in each group have different participant variables. A DV may actually have been caused by participant variables rather than the effects of the IV. The PVs may act as confounding variables which reduce the validity of the findings. To deal with this researchers use random allocation.
What is a repeated measures design? Give a limitation of it:
All participants take part in all conditions of the experiment.
Limitation:
Each participant has to do at least two tasks, with the order of these tasks possibly being significant (as doing a task first may have an influence on the second task).
Order effects can occur because repeating tasks can cause boredom or fatigue, or the participants skills may improve with repetition.
Demand characteristics can occur as participants are more likely to work out the aims of the task.
What is a matched pairs design? Give a limitation of it:
Pairs of participants are first matched on some variable(s) that may affect the dependent variable. Then one member of the pair is assigned to Condition A and the other to Condition B.
Limitation:
Participants can never be matched exactly, so differences between them may affect the DV.
Matching may be time consuming and expensive, especially if a pre-test is required.
What is random allocation?
An attempt to control for participant variables in an independent groups design which ensures that each participant has the same chance of being in one condition as any other.
What is counterbalancing?
An attempt to control for the effects of order in a repeated measures design: half the participants experience the conditions in one order, and the other half in the opposite order.
What are the 3 types of experimental designs?
- Independent groups design
- Repeated measures design
- Matched pairs design
What are labatory experiments?
An experiment that occurs in a controlled environment in where the researcher manipulates the IV, records the effect on the the DV and controls extraneous variables.
Give strength of laboratory experiments:
- High control over CVs and EVs- allowing the researcher to ensure any effect on the DV is likely due to the IV (cause and effect relationship).
- Replication is easier because of the high level of control, so we can ensure that new EVs are not introduced when repeating an experiment to ensure validity.
Give a limitation of laboratory experiments:
- Lack generalisability; they are not representative of everyday life.
- Labs are an artificial situation so cannot accurately assess how we would respond in a real life scenario (lacks ecological validity).
What are field experiments?
An experiment that takes place in a natural setting where the researcher manipulates the IV and records the effect of the DV.
Give a strength of field experiments:
Have ecological validity (not an artificial scenario, Ps may also not realise they are being studied)
Give a limitation of field experiments:
- Loss of control of CVs and EVs- making IVs and DVs harder to establish and replicate.
- Ethical issues- if Ps are unaware they are being studied they cannot give informed consent.
What is a natural experiment?
An experiment where the change in IV is naturally occurring, and the DV is decided by the researcher.
Give a strength of natural experiments:
- Allow for research to be conducted in situations where it may not have been undertaken for practical or ethical reasons e.g. Romanian Orphans.
- Often have high ecological validity.
Give a limitation of natural experiments:
- Naturally occurring IV events are rare, reducing research opportunities and limiting generalisability.
- Ps may not be randomly allocated to experimental conditions (when there is an independent groups design), so it is unsure if the IV has affected the DV. e.g In Romanian orphans the IV was whether they were adopted early or late, however other differences may arise in the two groups- later adopted children may have been less sociable, making them less appealing to adoptive parents.
What are quasi experiments?
An experiment that has a fixed IV based on the differences between people (e.g. age, gender), and the DV is decided by the researcher.
What is the difference between a natural and quasi experiment?
- Both experiments have an IV that is naturally occurring and out of the researchers control.
- Natural experiment: The IV is a naturally occurring EVENT or SITUATION that affects some people but not others. Groups are compared on something that has happened.
- Quasi experiment: The IV is a fixed DIFFERENCE between people (e.g. age, sex, diagnosis) where you are comparing types of people, NOT people affected by an event.
Give a strength of a quasi experiment:
Often carried out under controlled conditions, allowing for replication.
Give a limitation of a quasi experiment:
- Ps cannot be randomly allocated to conditions, so there may be CVs.
- The IV is not manipulated by the researcher, so we cannot claim that the IV has caused any observable change.
What is a pilot study?
- A small-scale version of an investigation that occurs before the real investigation is conducted.
- Aims to check that the investigation works, e.g. procedures, materials, and to identify any changes that need to be made.
What are single-blind procedures?
- Ps will not be told the aims of the research and other details e.g. the conditions of the experiment or if they are in a condition at all.
- Any information that may create expectations is not revealed until the end of the study to control the confounding effects of demand characteristics.
What are double-blind procedures?
- Neither the Ps or researcher who conducts the study are aware of the aims of the research.
- If all individuals do not know what materials/conditions are real then expectations cannot influence participant or researcher behaviour.
