Experimental Research

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Lecture 13

• Experimental Research

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Definition

• A research tool that allows scientists to find
  out whether a treatment influences (causes) a
  given behavior or mental characteristic by
  randomly assigning some participants to get the
  treatment and other participants to not receive
  the treatment.

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Three components of experiments

• 1. Manipulation
• Independent variables
• 2. Measurement
• Dependent variables
• 3. Random assignment (cf. random sampling)
• Each subject has an equal chance of being
  assigned to each treatment group

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Example

• Marijuana smoking lowers academic performance.

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Advantages of experiment(pp. 231-232)

• 1. Evidence of causality Experiment is valuable
  source of information because it is the only
  method that allows us to make causal statements
  (statements about what makes something happen
  statements about what factor influences another
  statements like "That behavior occurs
  because...." or "The effect of noise is ....").

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3 CANONS of causality(p. 223)

• 1. Time order causation is present if and only
  if the cause precedes the effect
• 2. Association between the 2 variables causation
  can occur only if some tendency for change in A
  results in change in B
• 3. Non-spuriousness all other alternatives must
  be ruled out (rival causes)
• Ex) RQ Does marijuana smoking lower academic
  performance?
• How to control rival causes? Experiments

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• 2. Control Researchers have control over the
  environment, the variables, and the subjects
• 3. Replication The conditions of the study are
  clearly spelled out in the description of an
  experiment.

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Disadvantages of experiment (p. 232)

• Artificiality
• Experimenter bias
• Limited scope
• Lack of external validity
• Subjects awareness of the testing situation

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Field experiments (pp. 244-250)

• The subjects function primarily in their everyday
  social roles with little investigator
  interference or environmental restructuring

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Advantages and disadvantages of field experiments

• External validity
• Nonreactive (subjects are not aware of being
  measured)
• Useful for studying complex social processes and
  situations
• Less expensive than laboratory experiments

• Ethics
• Unexpected external hindrances
• Time-consuming
• Cannot control all the intervening variables

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Online experiments (pp. 250-251)

• Conducting experiments on the Internet

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Advantages and disadvantages of field experiments

• Can access to a large and diverse sample
• Large sample size
• Can participate 24 hours a day, 7 days a week
• Cheaper
• More convenient for participants

• Lack of experimental control
• Subjects can cheat
• Participants are self-selected
• Technical problems
• Dropout rate is greater