EXPERIMENTAL DESIGNS

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EXPERIMENTAL DESIGNS
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Categories

• Lab experiments
• Experiments done in artificial or contrived
  environment
• Field experiments
• Experiments done in natural environment in which
  activities regularly takes place

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Lab Experiment

• Control
• When a cause-and-effect relationship between an
  independent variable and dependent variable of
  interest is to be clearly established, then all
  other variables that might contaminate or
  confound the relationship have to be tightly
  controlled
• Manipulation
• We create different levels of independent
  variables to assess the impact on dependent
  variable

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Controlling the Contaminating Exogenous or
Nuisance Variables

• Matching Groups
• To match the various groups by picking the
  confounding characteristics and deliberately
  spreading them across groups
• Randomization
• Distributing the confounding variables among the
  groups equally

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Internal Validity

• Refers to the confidence we place in the
  cause-and-effect relationship

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External Validity

• To what extent the results found in the lab
  setting be transferable or generalizable to the
  actual organizational or field settings?

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The Field Experiment

• Field experiments have more external validity,
  but less internal validity
• In the lab experiments, the reverse in true

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Factors Affecting Internal Validity

• History Effects
• Certain events or factors that would have an
  impact on the independent variable-dependent
  variable relationship might unexpectedly occur
  while the experiment is in progress, and this
  history of events would confound the
  cause-and-effect relationship between two
  variables

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Factors Affecting Internal Validity (Contd)

• Maturation Effects
• Cause-and-effect inferences can also be
  contaminated by the effects of the passage of
  time
• Testing Effects
• The fact that respondents were exposed to the
  pretest might influence their responses on the
  posttest

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Factors Affecting Internal Validity (Contd)

• Instrumentation Effects
• This might arise because a change in the
  measuring instrument between pretest and
  posttest.
• Selection Bias Effects
• Improper or unmatched selection of subjects for
  the experimental and control groups

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Factors Affecting Internal Validity (Contd)

• Statistical Regression
• When the members chosen for the experimental
  group have extreme scores on the dependent
  variable
• Mortality
• Mortality or attrition on the members in the
  experimental or control group or both

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Additional Threats to Internal Validity
Diffusion of treatment
Compensatory equalization
Compensatory rivalry
Resentful disadvantaged
Local history
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Factors Affecting External Validity

• The effects of the treatment will not be the same
  in the field
• Selection of the subjects

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Types of Experimental Designs

• Quasi-Experimental Designs
• No comparison between groups, nor any recording
  of the status of the dependent variable as it was
  prior to the experimental treatment and how it
  changes after the treatment
• Pretest and posttest experimental group design
• Posttest only with experimental and control group

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Types of Experimental Designs (Contd)

• True Experimental Designs
• Pretest and posttest experimental and control
  group designs
• Solomon four-group design
• Two experimental groups and two control groups

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Simulation

• An experiment conducted in a specially created
  setting that very closely represents the natural
  environment in which activities are usually
  carried on

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Ethical Issues

• Putting pressure on individuals to participate in
  experiments through coercion, or applying social
  pressure
• Giving mental tasks and asking demeaning
  questions that diminish their self-respect
• Deceiving subjects by deliberately misleading
  them as to the true purpose of the research

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Ethical Issues (Contd)

• Exposing participants to physical or mental
  stress
• Not allowing subjects to withdraw from the
  research when they want to
• Using the research results to disadvantage of
  participants, of for purposes nor their liking
• Exposing respondents to hazardous and unsafe
  environment

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Ethical Issues (Contd)

• Not debriefing participants fully and accurately
  after the experiment is over
• Not preserving the privacy and confidentiality of
  the information given by the participants
• Withholding benefits from control groups