Experiments

• What are experiments 


  the most common and best research method because we can establish a cause (IV) and effect (DV) link between 2 variables (the IV and DV). only method with a DV + IV (direct manipulation of the IV to see an effect on the DV. In an experiment we want the IV to be the only variable that causes an effect on the DV - any other EVs must be controlled
• What is the independent variable

  the variable manipulated by the researcher
• What is the dependent variable


  the variable being measured by the researcher
• What are extraneous variables


  any variable that we don't intend to study - they need to be controlled so that they don't become confounding
• Features of a lab experiment 


  • highly controlled environment/artificial setting which is specifically set up for the purpose of the investigation
  • manipulation of the IV
  • measure the DV
• Features of a field experiment 


  • natural everyday environment/setting
  • manipulation of the IV
  • measures a DV
• Features of a quasi experiment 


  • can be in a controlled or natural setting/environment
  • naturally occurring IV, no manipulation of IV
  • measures a DV
• Strengths of a lab experiment 


  • high levels of control over possible EVs = cause and effect can be established
  • highly standardised which allows replication of the study = ability to test for (internal) reliability/repeat the study
• Weaknesses of a lab experiment 


  • low ecological validity = hard to generalise to real life due to the artificial setting
  • high risk of demand characteristics (artificial so catch onto the aim) due to unnatural/unfamiliar setting = lack of internal validity
• Strengths of field experiments


  • high ecological validity as conducted in a natural setting = can generalise behaviour to real life
  • due to participants usually being unaware they are taking part, behaviour is more natural than in lab experiment so reduced demand characteristics = increased (internal) validity
• Weaknesses of a field experiment 


  • due to natural environment there will be poor control of EVs = lack of validity and so harder to establish cause + effect
  • due to natural environment there will be less standardisation = less able to replicate lowering (internal) reliability
• Strengths of quasi experiment 


  • enables you to study behaviour that would be unethical or not practical to manipulate e.g phobias = more insight in behaviour we couldn't study otherwise
  • quasi experiments still have high levels of control over EVs (as within lab experiment) = would be able to establish cause + effect
• Weaknesses of quasi experiment 


  • cannot randomly allocate Ps to conditions which may increase the risk of individual differences = lack of (internal) validity
  • quasi experiments are often conducted in labs so if the task is unnatural then the study could lack ecological validity = can't generalise to real life
• Features of independent measures


  • 2 or more experimental conditions + Ps only take part in one condition
  • Ps are randomly allocated to one of the experimental conditions
• Strengths of independent measures


  + no risk of order effects = increased internal validity

  + reduced risk of demand characteristics = increased internal validity
• Weaknesses of independent measures 


  high risk of individual differences affecting results = low internal validity
• Features of repeated measures 


  all Ps take part in all/both experimental conditions
• Strengths of repeated measures


  reduced/no risk of individual differences affecting results = increased internal validity
• Weaknesses of repeated measures


  high risk of order effects (fatigue, boredom, practice) = lack of internal validity

  high risk of demand characteristics = low internal validity
• Features of matched participants

  Ps are matched on key characteristics that could affect the results and then the each P in the pair is randomly allocated to one condition
• Strengths of matched participants


  + no risk of order effects = increased internal validity

  + reduced individual differences = high internal validity
• Weakness of matched pairs


  very difficult and time consuming to successfully put in place especially with larger samples = less economical
• What are order effects


  when the participant experiences more than one experimental condition and so their performance in the secondary condition is affected/change their behaviour due to taking part in another condition previously:

  fatigue (decrease score)

  boredom

  practice (improve/increase score)

  these confound results
• How to control order effects


  use counterbalancing if using repeated measures: the sample is divided in half with 1/2 completing the 2 conditions in one order and the other 1/2 completing them in the opposite order

  Use independent measures
• What are situational variables and how to control them


  Variables in the situation of the study which impact how participants behave

  Use lab experiment which had highly controlled artificial setting
• What are individual differences and how to control them


  Personal traits/characteristics of participants that impact their behaviour

  Use matched pairs or repeated measures design
• What are researcher effects and how to control them


  The way the researcher behaves can impact participants behaviour

  Standardised instructions

  A double blind procedure
• What are demand characteristics and how to control them


  When participants figure out the aim so change their behaviour to fit in line with it

  Independent measures

  Deception

  Single blind procedure

  Field experiment
• What is social desirability and how to control it 


  When participants change their natural behaviour to appear socially desirable

  Have participants complete task in a room on their own
• What is a single blind procedure


  Participants don’t know which condition they are in/the true aim
• What is a double blind procedure 


  The researcher and the participants are both unaware of what condition participants are in/the aim