Experimental methods

• In an experiment the researcher is trying to find out whether a particular factor has an effect on a specific aspect of human behaviour or mental process
• Laboratory experiments-

  -Conducted in a special environment where variables can be carefully controlled

  -Ppts usually aware that they are taking part in experiment although may not know true aims

  -Involves manipulation of IV
• Field Experiments-

  -Conducted in a more natural environment

  -Still a deliberate manipulation of variables by researcher, but is less likely that ppts know they are in experiment

  -Involves manipulation of IV
• Natural Experiment-

  -Conducted when it is not possible, for ethical or practical reasons, to deliberately manipulate an IV

  -IV varies naturally

  -DV may still be tested in a laboratory
• Quasi Experiment-

  -The IV is naturally occurring and the DV may be tested in a lab

  -Defining feature is that the IV has not been made to vary by anyone

  -Simply a difference that exists between people
• Mundane realism -

  -How realistic a research task is

  -Does it reflect real life
• Demand Characteristics-

  -Ppts change their behaviour due to them knowing the aim
• Internal validity-

  -The extent to which we can be confident that the IV affects the DV and not extraneous variables
• External Validity-

  The extent to which results can be generalised to other settings (Ecological), people (Population) or time (Temporal)
• Advantage of Lab study -

  -High control of external variables, establish cause and effect

  -High internal validity

  -Highly replicable
• Disadvantage of Lab study-

  -Lacks external validity, cant generalise findings to other settings

  -Tasks may lack mundane realism

  -Greater chance of demand characteristics
• Advantage of Field study -

  -Greater external validity than a lab

  -Less chance of demand characteristics
• Disadvantage of Field study-

  -Less control of extraneous variables, therefore cant establish cause and effect

  -May be ethical considerations

  -Not easy to replicate
• Advantage of natural study-

  -Allows research where IV can't be manipulated

  -Enables psychologists to study 'real' problems
• Advantages of Quasi study-

  -Allows comparisons between groups of people
• Disadvantages of Natural & Quasi experiments-

  -Can't establish cause + effect

  -Random allocation of ppts not possible

  -Can only be used when conditions vary naturally

  -Ppts may be aware that they're being studied

  -DV could still be an artificial task