experimental designs and the experimental method

• outline the experimental method


  Experiments involve a researcher manipulating a variable, known as the independent variable (IV). This results in a minimum of two conditions. They then measure what effect this has on a variable known as the dependent variable (DV). If there is a difference in the DV between the conditions of the IV, the researcher can establish cause and effect i.e. they can conclude that the manipulation of the IV caused an effect in the DV.
• what are the experimental methods

  • independent groups design
  • repeated measures desgin
  • matched pairs design
• independent groups design

  Different participants take part in each condition of the experiment. Used to compare one group against another.
• repeated measures desgin

  The same participants take part in all conditions of the experiment. Used to compare participants’ before and after performance.
• matched pairs desgin

  Different participants take part in each condition of the experiment. However,

  these participants are matched on key variables that could affect the dependent variable.
• Why do independent groups/matched pairs designs avoid order effects?

  🟢 Participants take part in only one condition, preventing practice, boredom, or fatigue effects, increasing validity.
• Why do repeated measures designs have a risk of order effects?

  🔴 Participants take part in all conditions, which may cause fatigue, practice effects, or boredom, decreasing validity
• Why do independent groups/matched pairs designs have better control over task variables?

  🟢 Participants only take part in one condition, so the same materials can be used without the risk of practice effects, improving validity.
• Why do repeated measures designs have less control over task variables?

  🔴 Different materials may be needed in each condition to avoid practice effects, which could affect results and decrease validity
• Why do independent groups/matched pairs designs reduce demand characteristics?

  🟢 Participants only take part in one condition, making it harder to guess the research aims and change behavior, increasing validity.
• Why do repeated measures designs increase demand characteristics?

  🔴 Participants take part in all conditions, making it easier to guess the study’s aims and alter behavior, decreasing validity.
• Why do independent groups designs have a high risk of participant variables?

  🔴 Different groups are compared, so differences between participants (e.g., intelligence, personality) may affect results, decreasing validity.
• Why do repeated measures designs eliminate participant variables?

  🟢 The same participants take part in all conditions, ensuring differences between groups don’t affect the results, increasing validity.
• Why do matched pairs designs attempt to control participant variables?

  🟢 Participants are matched on key traits, reducing individual differences between conditions and increasing validity.
• Why may participant variables still be an issue in matched pairs designs?

  🔴 It is difficult to match participants exactly on all key variables, meaning some differences could still affect results, decreasing validity.
• Why are matched pairs designs time-consuming?

  🔴 Large participant samples are needed, and matching takes time, delaying research and increasing costs.
• Why are independent groups designs time-consuming?

  🔴 Large samples are required since different participants take part in each condition, increasing research time and costs.
• Why are repeated measures designs the least time-consuming?

  🟢 Fewer participants are needed since they take part in all conditions, speeding up research and reducing costs.