reliability, validity, extraneous variables

• Reliability

  when the findings are consistent and can be repeated/replicated
• validity

  whether the study is well made and accurate.

  (is the study measuring what they should measure?)
• why is a lab experiment more reliable that a field experiment? (2 marks )

  1 mark - relating the r/v to an element

  A lab experiment is more reliable as the researcher has more control over variables leading to more reliable findings

  
  

  1 mark - explain how it increases/decreased the r/v

  This increases the reliability as the findings are more consistent and can be repeated
• why does a natural experiment has a higher validity than a field experiment?

  A natural experiment has higher validity as the experiment is in a natural setting meaning it reflects the real world. This increases the internal validity as it is measuring the right thing.
• Extreneous Variables

  extra aspects of an investigations that may affect the results of the DV
• order effects

  when participants either get better or worst at the 2nd condition due to tiredness or practice from the 1st condition
• social desirability

  when participants lie to make themselves feel better than they are
• 4 ways on how to reduce/control extraneous variables

  - randomization

  - random allocation

  - standardisation

  - counter balancing
• random allocation

  using chance to decide which group the participants go into
• what does random allocation do?

  lowers the chance of bias towards a particular group
• example of random allocation

  flipping a coin to decide who goes into which group
• Randomization

  using chance to design the materials used
• what does randomization do?

  reduces bias
• example of randomization

  pulling words out of hat for a word list for a memory experiment
• Counterbalancing

  one half completing the two conditions in one order and the other half completing the conditions in the reverse order.
• what does counterbalancing do?

  prevents order effects
• Standardisation

  keeping everything the same for every participant in all the conditions except for the IV
• what does standardisation do?

  helps identify that the changes in the DV are from the changes of the IV rather than extraneous variables
• example of standardisation

  the time of day, instructions given to participants etc.