Experimental method/types

• What is an aim?

  An aim is developed from a theory, a general statement that described the purpose of an investigation.

  
  

  e.g. To investigate whether drinking energy drinks makes people more talkative
• What is a hypotheses?

  A statement that is made to state the relationship between variables stated by the theory.

  E.g. Drinking an energy drink (Monster) causes people to become more talkative
• What are the two types of hypotheses?

  Directional and non-directional
• What is a directional hypothesis?

  The difference between the two variables is predicted and outlined. Usually includes 'lower/higher' 'more/less'

  E.g. People who drink monster become more talkative than people who don't
• What is a non-directional hypothesis?

  A hypothesis that simply states there will be a difference between conditions or groups but does not specify the difference.

  
  

  E.g. People who drink monster will differ in terms of talkativeness compared to those who don't
• What is an independent variable?

  The variable that is manipulated/changed to see its effect on the DV
• What is a dependant variable?

  The variable that is measured by the researcher. IV causes the effect on the DV
• Operationalisation


  Defining variables in terms of how they can be measured
• Experimental methods

  Lab experiment

  Field

  Natural

  Quasi
• What is a lab experiment?

  Takes place in a controlled environment

  Researcher manipulates IV and records effect on DV whilst maintaining strict control over extraneous variables
• What is a field experiment?

  Takes place in a natural setting

  Researcher manipulates IV and records effect on DV
• What is a natural experiment

  Change in IV is not brought about by researcher but would have happened even if the researcher had not been there. DV effect is recorded
• What is a quasi-experiment

  The IV is pre-existing (e.g. being old) and has not been determined by anyone
• Strengths of lab experiment


  • High control over extraneous variables, ensures effect on DV is likely the result of the IV manipulation
  • Replication is more possible due to high level of control, allows a direct measure of validity and ensures that there are no new extraneous variables during replication
• Limitations of lab experiment

  • Lacks generalisability, usually artificial stimuli and lacks mundane realism meaning ppts may behave unrealistically due to the formulated environment and therefore has low external validity/findings can't be applied to real-life situations
  • Demand characteristics, ppts are usually aware they are being tested and may increase unnatural behaviour, therefore may distort findings and conclusions derived from experiment
• Strengths and limitations of a field experiment

  • High mundane realism, uses a natural environment and ppts do not usually know they are being studied which may produce more naturalistic behaviour in ppts, therefore produces high external validity in findings/generalisations
  • Loss of control over extraneous variables, therefore cause and effect between IV and DV is difficult to establish. Replication to ensure findings may not be possible
  • Ethical issues behind ppts consent when being studied
• Strengths of natural experiment

  • Provides opportunities for research that may not be undertaken for practical or ethical reasons (E.G. RUTTER ROMANIAN ORPHANS)
  • High external validity due to the study of real-life issues and problems as the happen, findings are more relative to real-life and could be generalised
• Limitations of natural experiment

  • Rare opportunities for research, if involving a naturally occurring event this may happen rarely and therefore limit the scope for generalisations to other situations or similar studies to compare findings
  • Ppts can't be randomly allocated to experimental conditions, therefore researcher may not be able to establish the cause and effect between the IV and DV
• Strengths of a Quasi experiment

  • High control over extraneous variables, ensures effect on DV is likely the result of the IV manipulation
  • Replication is more possible due to high level of control, allows a direct measure of validity and ensures that there are no new extraneous variables during replication
• Limitations of a quasi experiment

  • Ppts can't be randomly allocated to experimental conditions, therefore may increase confounding variables that will affect the study of IV and DV interaction