Types of experiment

• A laboratory experiment is conducted in a controlled environment e.g. a lab

  • the researcher manipulates the independent variable and controls extraneous variables
• Strengths of laboratory experiments:

  • high control over extraneous variables → ensures only the IV affects the DV, making it easier to establish cause and effect
  • easily replicable → due to high control, results can be repeated in future studies to check reliability
• Weaknesses of laboratory experiments:

  • lacks ecological validity due to artificial setting which may not reflect real-life behaviour (low mundane realism)
  • may lead to demand characteristics → participants may guess the aim of the study and change their behaviour accordingly
• Field experiments are conducted in a natural environment (e.g. school, workplace), but the independent variable is still manipulated by the researcher.
• Strengths of field experiment:

  • higher ecological validity → participants behave more naturally compared to a lab setting (higher mundane realism)
  • reduced demand characteristics → participants may be unaware they are in an experiment.
• A weaknesses of field experiments:

  • less control over extraneous variables → other factors (e.g., distractions) could influence results, making cause and effect harder to establish.
  • ethical issues → participants may not have given full consent if they don’t know they are being studied.
• A natural experiment involves an independent variable that is naturally occurring (e.g. natural disaster), and the researcher does not manipulate it.
• A strengths of natural experiments:

  • allows study of real-world situations → useful for researching variables that cannot be ethically or practically manipulated (e.g., the effects of natural disasters on stress)
  • high ecological validity → real-life settings make findings more generalisable.
• A weakness of natural experiments:

  • no control over extraneous variables → other variables may influence results.
  • rare and unpredictable → natural occurrences cannot be scheduled and happen rarely, making studies harder to replicate and limits the scope of generalising the findings to other studies.
• A quasi experiment is when the independent variable is based on a characteristic or difference that already exists (e.g. gender or age). So, the researcher cannot randomly allocate participants to conditions.
• Strengths of quasi experiments:

  • useful when random allocation is impossible → Allows for research into areas that cannot be ethically manipulated (e.g., brain damage).
  • high control (sometimes) → if conducted in a controlled setting, extraneous variables can still be controlled.
• Weaknesses of quasi experiments:

  • no random allocation → participants are naturally divided, so participant variables may influence results.
  • confounding variables likely → differences between groups might not be due to the IV alone.
• The types of experiments include:

  • laboratory experiments
  • field experiments
  • natural experiments
  • quasi experiments
• Choosing the Right Type of Experiment

  • Laboratory → When control is needed for high reliability.
  • Field → When real-life behavior is the focus.
  • Natural → When the IV cannot be ethically or practically manipulated.
  • Quasi → When studying pre-existing differences (e.g., gender, mental health conditions).