Experiments

• Lab experiments:

  Tightly controlled environment

  Manipulated IV

  Measures DV

  Controls EV
• Lab experiment A03: STRENGTH

  I: high internal validity

  E: Tightly controlled conditions with manipulation of IV which means the researcher has high control over EVs

  C: Certain the only thing affecting the DV is the IV - measured what they intended to measure.
• Lab experiment A03: STRENGTH

  I: high reliability

  E: can be repeated easily and get the same result

  C: shows the findings were consistent.
• Lab experiments A03: WEAKNESS

  I: low ecological validity

  E: Artificial environment - participants may not act the same way they would in the real world

  C: affects the extent to which we can generalise the findings to the real world.
• Field experiments:

  • More natural environment
  • Manipulates IV
  • Measures DV
  • Controls some EVs
• Field experiment A03: STRENGTH

  I: high ecological validity

  E: accurately represents the real world and results can then be generalised

  C: results can be generalised to real world and used to develop practical applications or understand behaviour in the real world.
• Field experiment A03: STRENGTH

  I: fewer demand characteristics

  E: behaviour is more likely to be natural as they are less likely to guess the aim

  C: Adds internal validity as we can trust the DV has been affected by the IV
• Field experiments A03: WEAKNESS

  I: lack of control

  E: In a natural environment extraneous variables cannot be controlled

  C: If there are EVs tit cannot be guaranteed that the DV has been affected by the IV.
• Quasi experiments:

  • IV is based on existing difference, age or gender
  • tightly controlled environment
  • experimenter does not manipulate the IV
  • Measures the DV
• Quasi experiment A03: STREGNTH

  I: high reliability

  E: Done in a controlled environment meaning they can be done in the same way again and again

  C: results are accurate and can be repeated and be generalised to the real world
• Quasi experiment A03: WEAKNESS

  I: cofounding variables

  E: cannot randomly allocate participants to conditions so there may be cofounding variables like gender

  C: Low internal validity because we are not confident that the DV is a result of the IV as the cofounding variables may have affected the DV.
• Natural experiments:

  • Conducted in natural environment
  • no control over IV - naturally occurring
  • Measures the DV
  • has no control over EVs
• Natural experiment A03: STRENGTH

  I: high ecological validity

  E: Take place in real world so you will get data that is more generalisable to the real world

  C: Important as it means we can generalise the results to the real world and able to develop practical applications or explain real world behaviour.
• Natural experiments A03: STRENGTH

  I: fewer demand characteristics

  E: more likely to show real behaviours as they are less likely to know they are in a study

  C: confident that the DV has been affected by the IV.
• Natural experiments A03: WEAKNESS

  I: lack of control

  E: IV is not being directly manipulated which means there is a risk of extraneous variables

  C: affect internal validity as it could be affected by EVs and be unreliable.
• Independent measures design:

  Involves using different people in each condition
• Independent A03: STRENGTH

  I: low chance of order effects

  E: In both conditions - better through practice or worse through fatigue - only complete one condition

  C: only thing affecting the DV is the IV
• Independent A03: STRENGTH

  I: fewer demand characteristics

  E: take part in one condition so less likely to guess the aim

  C: confident the DV has been affected by the IV
• Independent A03: WEAKNESS

  I: individual differences

  E: different people so their performance could be affected by their personality/ intelligence

  C: cannot be confident the IV is affecting the DV as it could be extraneous variables
• Repeated measures design:

  same people part of both conditions
• Repeated A03: STRENGTH

  I: individual differences

  E: Only change between the conditions is the IV

  C: can determine a cause and effect relationship because individual differences are not affecting the DV.
• Repeated A03: WEAKNESS

  i: increased demand characteristics

  E: take part in both conditions so more likely to guess the aim of the study and then change their behaviour accordingly

  C: not truly measuring the behaviour of the participants meaning there is low internal validity
• Repeated A03: WEAKNESS

  I: order effects

  E: take part in two conditions - could get better in second condition through practice or worse through fatigue

  C: not confident the only thing affecting the DV is the IV
• Counterbalancing:

  ABBA method

  Half of participants take part in condition A and then complete condition B later

  the other half take part in Condition B and complete condition A later

  the ordering of the groups cancels out order effects
• Matched pairs design:

  different participants in each condition but matched with another participant who is similar in a number of variables

  Give them a pre-test - pair people up with similar scores - randomly allocate to different conditions + then compare
• Matched A03: STRENGTH

  I: reduced individual differences

  E: e.g. memory study that pairs people with their age in different conditions there will less affected by age

  C: only measuring impact of IV on DV and not impact of individual differences
• Matched A03: STRENGTH

  I: reduced demand characteristics and no order effects

  E: only taking part in one condition so will not get better or worse and are less likely to guess the aim

  C: only measuring impact of IV on the DV and not impact of individual differences.
• Matched A03: WEAKNESS

  I: individual differences still happen

  E: Although they are reduced everyone is different and it is impossible to match people perfectly in different conditions

  C: researcher cannot control individual differences meaning there will be low internal validity as cannot be sure the IV is affecting the DV