Experiments

• Lab experiments is where the researcher manipulates the IV to see the effect it has on the DV.

  + Extraneous variables can be controlled so the researcher can infer a cause and effect relationship (the IV is what caused the DV to change)

  + Experiment can easily be repeated

  _ Participants may not behave naturally due to controlled situations, reducing ecological validity as they may respond to demand characteristics

  _ Low mundane realism as the task may not represent everyday experience
• Field experiments take place in a natural environment, but still maintain some control over key variables. (Hofling's study of obedience in nurses which took place in hospitals).

  + Participants are unaware of the study taking place so there is a more natural reaction to the situation.

  + High mundane realism as it takes place in a natural environment

  _ Time consuming/expensive

  _ Less control over extraneous variables, therefore harder to ensure IV had effect on DV
• Quasi experiments are not true experiments as the IV cannot be directly manipulated or participants aren't randomly allocated to a condition (Driving ability between men and women).

  + Highly controlled, therefore more certain about demonstrating cause and effect.

  + Confounding variables are minimised which improves validity.

  _ Cannot claim IV caused any observed change
• Natural experiments is where the change in the IV is also natural. The experimenter studies a naturally varying IV rather than directly manipulating it.

  + Allows research of real problems as IV cannot be manipulated

  _ Can't control confounding variables

  _ Cause and effect cannot be certain
• Repeated measures is where the same participants are used in each condition.

  + No individual differences as same p's are used in each condition therefore observed changes are likely to be due to IV.

  + Need less p's overall, therefore less expensive/time consuming.

  _ P's may guess purpose of experiment by second condition (demand characteristics).

  _ Order effects may occur (practice, boredom, fatigue) although this can be reduced by counterbalancing.
• Independent groups is where different participants are randomly allocated to one condition.

  + P's less likely to guess purpose of experiment

  + No problem of order effects

  _ Individual differences may affect results

  _ Need more P's to obtain all data
• Matched pairs is where different participants are used for each condition, but they have been matched on important characteristics for that study.

  + Some important participant variables are controlled for

  + P's less likely to guess purpose of experiment

  _ Time-consuming to match p's
• counterbalancing reduces effect of situational variables or order effects.
• Situational variables (order effects, time of day, temperature) could influence P's behaviour
• Demand characteristics could result in social desirability bias.
• Single blind is where the p's are unaware of which condition they are in.
• Double blind is where the researchers and p's don't know which condition they are in.
• A pilot study is done before carrying out the actual study, to find out if certain things don't work (p's may not understand instructions). This allows the researcher to make adjustments before carrying out the real study.
• Randomisation is the use of chance methods to control for the effects of bias.
• Standardisation is using exactly the same formalised procedures and instructions for all p's in a research study.