Experimental Methods

Laboratory Experiment

Conducted in high controlled environment, not always in a lab. Researcher manipulates the IV, records the DV. Maintain strict control of extraneous variables. Participants know what they’re apart of, may not know the true aims

First strength of laboratory experiments

P - Replication is more possible since there are high levels of control. E - Carefully designed, well carried out, clearly reported to see if there are similar results. No new EVS due to high levels of control. L - Similar findings = reliable, increased confidence. Replication is vital to check results of any study to see if the finding is valid

Second strength of laboratory experiments

P - High internal validity. E - Easier to control EVS in a lab than other research settings or with any other research method. L - If the other variables (not IV) are controlled, can be certain about showing cause and effect

First limitation of laboratory experiments

P - Low ecological validity, may lack generalisability. E - May be artificial, not like everyday life. High levels of control. Participants may behave unusually, their behaviour can’t be generalised beyond the setting. L - Artificial nature can cause issues with generalising findings to everyday life = low external validity

Second limitation of laboratory experiments

P - More prone to demand characteristics. E - Participants are usually aware they are being tested, could cause “unnatural behaviour”. L - Demand characteristics can threaten internal validity, experiment may not measure what it wants to

Field experiments

Conducted in a more natural, everyday setting. Participants may not know they are participating in an experiment

First strength of field experiments

P - High ecological validity. E - Done in real life settings, may produce more authentic behaviour. L - Researchers can generalise their findings beyond the research setting = high external validity

Second strength of field experiments

P - Lead to a reduction in demand characteristics. E - Participants not be aware they are apart of an experiment, so they don’t change their behaviour. L - Increases internal validity

First limitation of field experiments

P - Lower internal validity. E - Loss of control of EVs from increased realism. Precise replication isn’t often possible. L - May not establish cause and effect from the difficulties of reaching high levels of control. Difficult to exactly repeat the experiment for the same results, the conditions are never exactly the same

Second limitation of field experiments

P - Can raise major ethical issues. E - Difficult to debrief them if participants don’t know they are being studied. Recoding behaviour and manipulation = ethical issues. L - Unethical if participants don’t give informed consent. Some research can create an invasion of privacy

Natural experiments

Researcher doesn’t manipulate the IV, IV is naturally occurring. Compare behaviour before and after or with a control group. Conducted when manipulation is unethical or impractical

First strength of natural experiments

P - High ecological validity. E - No manipulation of the IV. L - Results are more likely to show true behaviour due to the setting. Results can be generalised beyond the setting = high external validity

Second strength of natural experiments

P - Provide opportunities for research that may not be taken for practical or ethical reasons, E - Such as the studies of institutionalised Romanian orphans. L - Makes them a key experimental method

First limitation of natural experiments

P - Difficult to replicate. E - The naturally occurring study the researcher wants to study is rare. L - Reduces opportunities that are available, can’t check the reliability of the results

Second limitation of natural experiments

P - Low in internal validity. E - The IV isn’t manipulated. Overall control is less than lab or field experiments. Increases the chance of confounding variables. L - Researcher can’t be confident that the outcome is due to the IV. Difficult to see cause and effect

Quasi Experiments

Pre-existing IV is a difference between people, can’t be manipulated. Researcher examines the effect of IV on the DV. “Almost experiment”, IV isn’t varied. IV is naturally occurring, DV may be measured in a lab

First strength of quasi experiments

P - Enables comparisons between different people. E - Researcher takes avantage of pre-existing conditions. L - Useful to where it could be impractical or impossible to manipulate variables

Second strength of quasi experiments

P - Carried out under controlled conditions. Share the same strengths as lab experiments. E - In a lab there are high levels of control, easy to control EVs. L - High internal validity due to a conducted experiment. Replication can happen

First limitation of quasi experiments

P - Participants can’t be randomly allocated to research conditions. Doesn’t remove the issue of bias. E - Confounding variables may not be able to be controlled. L - Reduces internal validity. Researcher can’t be confident of the outcome of the IV. Difficult to see cause and effect

Second limitation of quasi experiments

P - Can share the same limitations as lab experiments (both in controlled conditions). E - E.g participants may be aware they are being studied, prone to demand characteristics. L - Demand characteristics threaten internal validity