Methodological%20Evaluation%20of%20Experiments

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Methodological Evaluation of Experiments

• By Mr Daniel Hansson

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Important Concepts

• Reliability
• Replicability
• Validity
• Ecological validity
• External validity
• Internal validity
• Confounding Extraneous variables
• Control

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Reliability

• Reliability The extent to which an experiment
  yields the same result over repeated trials
• Replicability The ability of a test to be easily
  replicated

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Questions

1. How reliable would you say that the results of
   your study were?
2. How standardized were the procedures of the
   study? Is the study easily replicated?

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Validity

• Validity Whether you measure what you are
  supposed to measure
• Ecological validity The extent to which research
  findings can be applied to real life
• External validity The extent to which a research
  finding can be generalized to persons, settings,
  or times other than those that were the subject
  of study.

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Validity Activity

• 1. Take the IQ test at www.intelligencetest.com
  How valid do you think that the results were?
  Motivate your answer.
• 2. How well do you think that the results of your
  study could be generalized to people of other age
  groups or from other cultures?
• 3. Do you think the results of your study can be
  applied to real life situations?

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Internal Validity

• Internal validity Whether there were
  confounding/extraneous variables that attributed
  to the results
• Confounding/extraneous variables Variables other
  than the independent variable that may affect the
  independent variable. Confounding variables are
  variables related to the design of the
  experiment, extraneous variables are usually
  related to participants
• Control A variable in the experiment that is
  kept constant (the same) for all participants to
  improve internal validity. E.g. Same treatment,
  same/clear instructions, same gender, same age

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Examples of Confounding Variables

• Experimenter effect Researchers bias may cause
  them to unconsciously influence the participants
  of the experiment
• Demand characteristics When participants form an
  interpretation of the experiments purpose and
  unconsciously change their behavior accordingly

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Questions

1. What were the controls in your experiment?
2. Think of all the possible confounding variables
   that could have affected the internal validity of
   your experiment