Experiments

• A lab experiment takes place in a highly controlled environment which is artificial and set up specifically for the use of the investigation.

  You manipulate the IV and measure the DV.
• Strength of lab experiments

  • High levels of control over possible extraneous variables so cause and effect can be established. This causes high internal validity as we are measuring what we set out to.
  • Highly standardised which allows for replication of the study this leads to high internal reliability.
• Weaknesses of lab experiments

  • Low ecological validity so it is hard to generalise to real life due to the artificial setting. This reduces the usefulness and our ability to create practical applications.
  • High risk of demand characteristics due to unfamiliar setting leading to a lack of internal validity.
• A field experiment takes place in a natural everyday environment and is not controlled by the researcher.

  You manipulate the IV and measure the DV.
• Strengths of field experiments

  • High ecological validity as conducted in a natural setting so we can generalise behaviour to real life.
  • Behaviour can be more natural than lab experiments which increases internal validity.
• Weaknesses of field experiments

  • Harder control of extraneous variables due to the natural setting which decreases internal validity and makes it hard to establish cause and effect.
  • Natural environment means that there will be less standardisation so we can't replicate it leading to low internal reliability.
• A quasi experiment can be in a controlled or natural environment.

  It has a naturally occurring IV (e.g. gender) and you measure the DV.
• Strength of quasi experiments

  • Enables you to study behaviour that would be unethical or impossible to manipulate giving us more insight into behaviour. Leading to high usefulness as we can develop practical applications.
  • Can have high control over extraneous variables (when in controlled environments) so we can establish cause and effect due to high internal validity.
• Weaknesses of quasi experiments

  • Cannot randomly allocate participants to conditions which may increase the risk of individual differences leading to a lack of internal validity.
  • If conducted in a controlled environments, lack of ecological validity so we can't generalise our findings to real life.
• Independent measures is when different participants are randomly allocated to one of the experimental conditions.

  :) Reduces the risk of order effects such as fatigue. This increases internal validity.

  :( Increases the risk of extraneous variables as participants are only doing one condition. This decreases internal validity.
• Repeated measures is when all participants take part in all experimental conditions.

  :) Reduced risk of individual differences impacting the results as ppts do all conditions. Increases internal validity.

  :( Large risk of order effects as thy are completing a task more than once. This reduces internal validity.
• Matched participants is when participants are matched on a variable of interest, such as gender, age, or personality and these groups are equally distributed to each condition.

  :) Controls for individual differences as they are matched on their traits while also preventing order effects. This increases internal validity.

  :( Time consuming and often impractical to match participants based on their individual differences.