Experimental Methods Flashcards
What is a Laboratory experiment?
Carried out in a controlled environment, where the researcher manipulates the IV and measures the effect on the DV
What are strengths of using a lab experiment?
- Possible to determine cause and effect relationship between IV and DV
- Controlled environment allows great control over extraneous variables - ensure high internal validity
- Replication is easy - check for reliability
- Participants agree to take part, consent less of an issue (deception may prevent informed consent)
What are limitations of using a lab experiment?
- Artificial setting of lab means research may lack ecological validity, making it difficult to generalise results to other settings
- Being in a lab means participants are aware they’re being observed, making demand characteristics more likely which may lower the internal validity
- Fact people are being tested on how they perform on a task increases the likelihood of evaluation apprehension - again, effect behaviour and have an effect on the internal validity
What is a field experiment?
An experiment that takes place in a natural setting where the experimenter manipulates the IV and measures the DV
What are the strengths of using a field experiment?
- Ecological validity is easier to achieve as the setting is not artificial, more likely to generalise to other settings
- Participants are often unaware they’re involved in an experiment and will not respond to demand characteristics
- IV still manipulated by the researcher, so cause and effect can still be established
- Replication is SOMET|MES possible, as long as the environmental circumstances do not change too much, reliability can sometimes be checked (not as easily as in lab)
What are limitations of using a field experiment?
- The researcher does not have control of the setting, so there is a greater chance of confounding variables, making it less likely the experiment has internal validity
- Difficult to replicate (precise circumstances may not occur twice) so may be difficult to check the reliability of the findings
- Difficult to carry out using complicated apparatus
- May be more time consuming if researcher has to wait for the right time of day, right number of people, type of people etc
- Participants usually unaware they are taking part in an experiment, consent is difficult to obtain, debrief may be hard to carry out etc, ethical issues.
What is a quasi experiment?
An experiment often conducted in controlled conditions where the IV simply exists so there can be no random allocation to the conditions (may be referred to as not a true experiment) - No control condition, simply a comparison condition
What are the strengths of using a quasi experiment?
- Enables the investigation of variables that, for either practical or ethical reasons, cannot be manipulated by the researcher
What are the disadvantages of using a quasi experiment?
- There is less control over extraneous variables (e.g. participant variables) so there is a greater chance that these will confound the results - validity harder to achieve
- Because the IV is not manipulated by the researcher, cause and effect relationships cannot be concluded
What is a natural experiment?
An experiment where the change in the IV already exists naturally, rather than being manipulated by the researcher
What are the strengths of using a natural experiment?
- Enables the investigation of variables that for either practical or ethical reasons, cannot be manipulated by the researcher
- Often the ecological validity is high, as the setting is the real world, and it is real events that are being studied
What are limitations of use a natural experiment?
- Less control over extraneous variables (e.g. participant variables), so there is a greater chance that they will confound the results, internal validity harder to achieve
- Because the IV is manipulated by the researcher, cause and effect relationships cannot be concluded
- As they rely on naturally occurring events, they are difficult to replicate, so it is hard to check for reliability
- May be ethical issues which need to be controlled
What is repeated measures design?
An experimental design where each participant takes part in both/all conditions of the IV
What are the strengths of using RM design?
- Participant variables are controlled - helps to increase the internal validity
- Fewer participants are needed - reduces time and expense
What are the limitations of using RM design?
- Possibility of order effects - participant may get better through practice OR performance get worse due to fatigue or boredom
- Participants may be able to guess the purpose of the experiment as they’re exposed to both conditions of the IV - performance may change due to demand characteristics
- Inappropriate design if participation in one condition would affect the response in the other condition (deception involved)
- Some experiments its impossible for participants to be in both conditions e.g. sex differences
How are order effects controlled?
Counterbalancing - half participants do condition A then B, other half do B, then A, any order effects should cancel each other out
What is independent groups design?
An experimental design where each participant only takes part in one condition of the IV