types of experiment - research methods

What is a lab experiment

What is a lab experiment

This is an experiment that takes place in a highly controlled environment.- (this is not always in a lab ) within which the researcher manipulates the IV and records the effect on the DV, whilst maintaining strict control of extraneous variables

what is a strengths of a lab experiment ?

• they have high control over confounding variables and extraneous variables

• researchers are able to ensure that the change in DV is likely to be caused by the IV -

• more certain about demonstrating cause and effects (high internal validity

• replication is more possible = high levels of control

• ensures new extraneous variables are not introduced when repeating an experiment

• replication is vital to check results of any study to see whether the finding is valid or just a one-off

What are the disadvantages of lab experiments ?

• they may lack generalisability - experiment may be too artificial and not likely in everyday

• in an unfamiliar environment participants may behave in unusual ways so their behaviour cannot be generalised beyond the research setting (low external validity )

• Participants are usually more aware that they being tested in a lab experiment and this may cause unusual behaviours i.e. demand characteristics
  

What is a field experiment ?

an experiment that takes place in a natural setting within which the researcher manipulates the IV ( more everyday setting) and records the DV

What are the strengths of a field experiment ?

Higher mundane realism than lab experiments because the environment is more natural

thus the field experiments may produce behaviour that is more valid and authentic

especially the case when Ps are unaware they are being studied = high external validity

What are the limitations of field experiments ?

there is a loss of control of the Confounding variables (CVs) and extraneous variables (EVs)

This means the cause and effect between the IV and the DV may be more difficult to establish

a precise replication of these studies are often not possible

ethical issues may arise- if Ps are unaware that they are being watch (Covert observation) then they cannot consent to the being studied -such research =invasion of privacy

What is a natural experiemnt ?

an experiment when the change in the IV is not brought about but the researcher but would have happened even if the researcher was not there. (after a natural disaster or whether a child is in hospital )

Researcher records the effect on the DV this can be both naturally occurring or devised by the experimenter - then measured in the field or lab

What are the strengths to a naturally occuring experiment ?

they provide opportunities for research that may not otherwise be undertaken due to practical and ethical reason i.e. the 9/11 memory test or institutionalisation in the romanian orphans study

they have high external validity because they involve the study of real world issues and problems as they happen e.g. the effect of natural disasters on stress levels

What are the limitations to natural experiments ?

naturally occurring events may happen very rarely, reducing the opportunity for research - may also limit the scope for generalising the findings to other similar situations

Ps may not be randomly selected to experimental conditions - researcher are less sure if the IV effect DV

e.g. romanian study was whether the orphans were adopted late or early however there were lots of different factors between the groups such as those who were adopted late may also have been less sociable that some other children = less appealing to prospective parents

demand characteristics may be an issue

What is a quasi experiment ?

this is when the IV has not been determined by anyone - the variable simply exists i.e. age or sex

strictly speaking this is not an experiment

as with a natural experiment the Dv can occur either naturally e.g. exam results or may be devised by the experimenter and measured in a field or a lab

what are the strengths of quasi experiments ?

these are often carried out under controlled conditions and therefore share some strengths of a lab experiment e.g. easily replicated and

What are the limitations of quasi experiments ?

they cannot randomly allocate participants into conditions so there may be confounding variables

the iv is not deliberately changed by the researcher and therefore we cannot determine that the iv has caused any observed changes