Types of experiment

• Independent variable is the variable that is manipulated by the researcher between each condition of the experiment / study.
• Dependent variable is what is measured by the manipulation of the IV.
• Lab experiment takes place in an environment of high control where the researcher has control over all variables in the study.
• Strengths of lab experiments:

  • 'Cause and effect' can be established - Researcher holds all variables outside the IV and DV consistent allowing for manipulations in the IV to be observed by the changes in the DV.
• Strengths of lab experiments:

  • Replication - Lab experiments are easily replicated due to the use of standardised procedures.
• Strengths of lab experiments:

  • High internal validity - Any outcome of the DV is directly due to manipulation of the IV.
• Limitations of lab experiments:

  • Lacks ecological validity - High degree of control makes the study very artificial so it can not be applied to real life (lacks mundane realism).
• Limitations of lab experiments:

  • Experimenter bias - Unintentional influence of the of the experimenters expectations on the outcome of the study.
• Limitations of lab experiments:

  • Demand characteristics - Participants are aware they are in a study and may alter their behaviour to match the aim.
• Field experiments are conducted in more natural environments but with variables being very well controlled.
• Strengths of field experiments:

  • High ecological validity - Naturalistic environment encouraging more natural behaviours.
• Strengths of field experiments:

  • Mundane realism - Tasks used are less artificial and closer to the types of activities participants may usually carry out.
• Strengths of field experiments:

  • Less demand characteristics - Participants are unaware they are in a study so will not be changing their behaviour to match the aims of the study.
• Limitations of field experiments:

  • Ethical considerations - Invasion of privacy and likely to have no informed consent.
• Limitations of field experiments:

  • Loss of control - Extraneous variables could influence the measurement of the DV making precise replication not possible.
• Limitations of field experiments:

  • Random allocation - Impossible to assign roles which could result in a change in the DV that is due to participant variables.
• Natural experiments are when there is no set IV due to them occurring naturally in the real world without the influence of the researcher (eg reactions to earthquakes).

  Researcher records change in the DV between the levels of IV.
• Strengths of natural experiments:

  • Provides opportunities - Allows research to be conducted in areas where it would not have been possible due to ethical or cost reasons.
• Strengths of natural experiments:

  • High external validity - Natural experiments show examples of real behaviour occurring in the real world, free of demand characteristics.
• Limitations of natural experiments:

  • Naturally occurring events - Experiments are harder to replicate and generalise due to the rarity of the situation.
• Limitations of natural experiments:

  • Loss of control - Extraneous variables are harder to control and so the researcher can not establish a 'cause and effect'.
• Quasi experiments occur when an IV has not been established by the researcher as it naturally exists (eg gender studies).
• Strengths of quasi experiments:

  • Studies factors of already existing characteristics of participants.
• Limitations of quasi experiments:

  • Confounding variables - Allocation of roles are not possible and there may be other factors resulting in the change to the DV. This means a specific cause and effect can not be established as multiple things are having an effect on the DV.