types of experiments

• Quantitative methods

  • use data that cen be counted
• Qualitative methods

  • data that can be expressed in words and non-numerical
• Experiments:

  • use quantitative data
  • look at a measureable change in the DV which has been caused by different levels of IV
  • All experiments have an IV and DV
• Laboratory experiments

  • experiments conducted in a controlled environment
  • experimenter manipulates the IV and controls what happens
• Strengths of Laboratory

  • EV's can be controlled
  • Researcher can be sure the IV casued the DV so this can establish a cause and effect
  • Standardised Procedures can be used so the study is easy to repeat to test validity of results
• Weakness of Laboratory

  • Environment is not like everyday life due to artifical situation so it is difficult to generalise resluts to wider life because participant behaviour is less typical
  • Participants know they are being observed and tested so they change their behaviour to help the experimenter so may not act naturally – demand characteristics.
  • Data may not be valid
• Field experiments

  • conducted in a real or natural setting
  • experimenter manipulates IV
• Strength of field:

  • Often more realistic than lab experiments as participants not aware they are being studied – higher validity.
  • Participants don’t often realise they are being studied so will act naturally.
  • some control over EV because standardised procedures can be used so cause and effect conclusions are more valid
• Weakness of field:

  • Less control of extraneous variables (EV) because of real life setting so its more difficult to show cause and effect
  • There may be ethical issues – did participants give permission? May not know they are involved in experiment
  • Cannot give informed consent
• Natural experiments:

  • in natural or laboratory setting
  • The occurs in real life situation in which IV varies naturally, so no manipulation is needed by the researcher.
• Strengths of natural:

  • High validity as they involve real life changes- variables are naturally occuring but this isnt always the case
  • Generalisable to everyday situations
  • DV often tested in lab - EV can be well controlled because standardised procedures can be followed
• Weakness of natural:

  • Few opportunites for this kind of research as it relies on natural events . Reduces usefulness of the methid
  • Events may be rare that the researcher is interested in so replication is almost impossible. i.e. 9/11 or bank robberies
  • No control of extraneous variables e.g unique characteristics can not be controlled because they cannmot be randomly allocated to groups