Experiment

• Experimental Research


  • Purpose: To determine whether a cause-and-effect relationship exists between two variables.
  • Characteristics:
  • Generates numerical data.
  • Uses statistical tests to rule out the role of chance.
• Independent Variable (IV)


  • The variable manipulated by the researcher.
  • Example: Noise (dissonant rock music played at 100 decibels).
• Dependent Variable (DV)


  • The variable is measured after the manipulation of the IV.
  • Example: Number of words recalled from a list of 30 words.
• Controls


  • Ensure all other variables remain the same across conditions.
  • Examples: Same list of words, identical room conditions, same test time.
• Operationalization


  • Defining variables clearly for measurement.
  • IV: Noise as dissonant rock music at 100 decibels.
  • DV: Number of words remembered from a list of 30 words.
• Standardization


  Detailed procedures that allow for replication by another researcher.
• Random Allocation


  • Participants have an equal chance of being assigned to experimental or control conditions, reducing individual characteristic influences.
• Experimental Hypothesis


  • Predicts the relationship between IV and DV.
  • Example: Listening to dissonant rock music at 100 decibels will decrease the number of words recalled by adolescent girls from a list of 30 words.
• Null Hypothesis


  • States that the IV will have no effect on the DV, or any change will be due to chance.
  • Example: Listening to dissonant rock music at 100 decibels will have no significant effect on the recall of words by adolescent girls from a list of 30 words.
• Quasi-Experiments


  • Experiments where participants are grouped based on a trait or behavior, not randomly allocated.
  • Example: Comparing memory recall between people diagnosed with depression and those without.
  • Random Allocation: Not used in either quasi or natural experiments.
  • Causation: Do not show direct causation but can imply a causal relationship between IV and DV.
• Natural Experiments

  • A subset of quasi-experiments where the independent variable is environmental and outside the researchers' control.
  • Design: Often pre-test, post-test.
  • Example: Measuring clinical depression in Prague before and after a smoking ban in bars and restaurants.
  • Random Allocation: Not used in either quasi or natural experiments.
  • Causation: Do not show direct causation but can imply a causal relationship between IV and DV.
• Controlling Variables


  • Goal: Control as many variables as possible to ensure validity.
  • Extraneous Variables: Unwanted variables that can influence the IV and DV relationship.
• Artificiality


  • When the experimental situation is so unnatural that it questions the validity of the findings.