Experiments

• Keywords of Experiments

  • IV

  • DV

  • Extraneous Variables

  • Lab Experiment

  • Controls

  • Individual Differences

  • Independent Measures

  • Repeated Measures
• What does it mean to be an experiment?

  • Experiments are looking to establish a cause-and-effect.

  • They do this by possibly manipulating one variable and measure the other.
• What is an IV?

  IV - the variable we change/ manipulate.
• What is a DV?

  DV- The variable we measure.
• Lab Experiment

  Environment: Artificial or highly controlled.

  IV: Manipulated by the researcher.

  • Researcher assigns participants to conditions.
• Strength of Lab Experiment

  • High levels of control over extraneous variables SO allows to establish a cause-and-effect between the IV and DV.
• Weakness of Lab Experiment

  • Artificial setting SO may reduce ecological validity.

  • Aware of the study, increasing demand characteristics SO reduced validity.
• Field Experiment

  Environment: Natural

  IV: Manipulated by the researcher.

  • Participants usually don’t know they are taking part in the study.
• Strength of Field Experiment

  • High in ecological validity due to natural behaviour SO findings can be generalised to real life situations.

  • Low chance of demand characteristics SO increases internal validity.
• Weakness of Field Experiment

  • Low levels of control therefore many extraneous variables. This causes difficulty finding cause-and-effect reducing internal validity.
• Quasi Experiment

  IV: Naturally occurring.

  • Participants cannot be assigned randomly by researcher.
• Strength of Quasi Experiment

  • Can investigate unique IV‘s which may be unethical to manipulate SO we can gather more insight.
• Weakness of Quasi Experiment

  • Naturally occurring IV cannot randomly allocate in conditions SO high risk of individual differences.
• What is an order effect?

  Participation in one condition effects performance in the other e.g. practice

  effects or fatigue.
• What is Counterbalancing?

  When the order the participants complete the conditions in is varied e.g. half complete the control condition first while the other half complete the experimental condition first.
• Single Blind Technique

  • Reduces demand characteristics.

  • Participants don’t know they are taking part.
• Double Blind Technique

  • Reduces demand characteristic and researcher bias.

  • Both researcher and participants don’t know they are in it.
• Pilot Study

  A small scale trial of the study to determine the suitability of the procedure.
• Independent Measures

  • Randomly allocation of participants into ONE condition. (e.g. group 1 or 2.)

  • You will then measure the DV for each of the groups and compare the results of the 2 groups.
• Strength of Independent Measures

  • No risk of order effects.
• Weaknesses of Independent Measures

  • High risk of Individual Differences

  • Each person is only used once SO inefficient use of participants.
• Repeated Measures

  • All participants complete both conditions (e.g. both group tasks.)

  • You then compare results for the 2 conditions.
• Strength of Repeated Measures

  • No risk of Individual Differences.

  • Each person is used more than once SO efficient way of using participants.
• Weakness of Repeated Measures

  • High risk of order effects.

  • More prone to increased Demand Characteristics.
• Matched Participants

  • Participants gathered are matched with another person with similar and key variables such as age.

  • Each pair are then placed in one condition each.

  • They will then compare the results for each pair in the study.
• Strength of Matched Participants

  • No risk of Order Effects.

  • Reduces the effect of Individual Differences.
• Weakness of Matched Participants 


  • Hard to put into place due to having to measure and identify suitable criteria’s.
• What is an extraneous variable?

  Any factor which is not the IV which can affect the outcome of our DV.
• What are situational extraneous variables?

  Environmental factors that may affect the participants behaviour.

  • Temperature or noises.

  • Control by keeping the environment the same for all participants.
• What is participant extraneous variables?

  Any differences between each participant not accounted for in the IV.

  • Age, gender, mood or intelligence.

  • Control by having a large sample size to reduce participant variables OR use a matched pairs design.