Experiments

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Laboratory Experiment

Definition: Conducted in an artificial environment in an attempt to control all of the variables

Advantages

  • High levels of control limit effects of confounding variables
  • Replication is possible to test for reliability
  • Causal relationships can be made

Disadvantages

  • Results lack ecological validity because of the artificial environment
  • Participants may show demand characteristics because they know they're being studied
  • If deception is needed to allow a realisitc reaction ethical issues may be involved as the Pps did not give informed consent
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Field Experiments

Definition: Behaviour studied in natural environment but the IV is still manipulated

Advantages

  • High ecological validity as is conducted in a natural environment
  • Pps are usually unaware they're being studied so do not show demand characteristics

Disadvantages

  • Lack of control means that confounding varaibles are more likely to have an effect and a causal relationship is harder to establish
  • Ethical issues can be a problem because Pps have not usually given informed consent and don't know they're being studied
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Natural/Quasi Experiments

Definition: IV is not directly manipulated as is naturally occuring eg. gender, criminal record, age

Advantages

  • Makes relationships ethically possible to investigate as the IV is naturally occuring

Disadvantages

  • There is no control over extraneous variables so a causal relationship is hard to establish
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Independent measures design

Definition: Different Pps are allocated randomly to each condition of the experiment

Advantages

  • No order effects - practise or fatigue
  • Pps less likely to figure out what the experiment is about so less likely to have demand charactertistics

Disadvantages

  • More Pps are needed to find to participate which is time consuming
  • Participant variables may effect results - Pps in one condition may have a trait which advantages them above others
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Repeated Measures

DefinitionThe same Pps are used in all conditions

Advantages

  • Fewer Pps are needed so it saves time
  • Participant variables are prevented as same in each condition

Disadvantages

  • Order effects may influence results either by practise or fatigue
  • Pps may work out what the experiment is about and show demand characteristics
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Matched Pairs

Definition: Pairs of participants are closely matched on characteristics and then randomly allocated to one of the conditions

Advatages

  • Reduces participant variables effecting results as characteristics matched
  • Avoids order effects as different Pps used

Disadvantages

  • Matching and finding pairs is very time consuming and can be difficult
  • It is impossible to match each pair completely so participant variables may still have an effect
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Aims, variables + Hypotheses

Aim - The purpose of the study

Hypotheses:

  • Directional = a prediction of a specific outcome. Saying the independent will affect the dependent in a specific way
  • Non-directional = a general prediction of the outcome. Saying the independent will affect the dependent but not how
  • Null = a predicition that the independent will have no affect on the dependent

Variables

Something which can vary within a study

  • Independent = variable which is manipulated
  • Dependent = variable which is measured
  • Extraneous/confounding = Uncontrolled variable which may have affected the dependent
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