Chapter 9 Lecture 8

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Chapter 9 Lecture 8
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Some ways to control threats

• General control procedures
• Control over subject and experimenter effects
• Control through participant selection and
  assignment
  
• Control through specific experimental design

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1. General Control Procedures
Control over research setting
Lab internal validity --generalization
Applied setting --internal validity generaliza
tion

• Natural environment
• In the lab
• Stanford Prison Experiment

- the psychological effects of becoming a
prisoner or prison guard. - set up a simulated a
prison

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Planned simulation of 2 weeks (1971)
N 24 college students from the U.S.
15/day by participating in a study
Flip of coin? prisoner guard
basement of Stanford's Psychology Department
building
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• Response Measurement
• Focus on the DV careful selection of the
  measurement
  
• make sure measure is validated (scale)reliable
• (scale development)

Replication Pilot experiment Exact replication
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2. Control over Subject Experimenter effect
- motivation
- knowledge - expectations
?blind double blind procedures
Experimenter knows the hypothesis, subject assig
nment etc
Blind research assistant blind to assignment
into a group Double Blind both RA Subje
ct do not know (drug
studies/ light therapy)
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• Automation
• reduce experimenter/subject contact
• (tape recording etc) instructions
• computer testing
• Objective measures (subjective DV)
• stereotyping/prejudice/in group/out group (RT)
• Multiple observers multiple experimenters
• interrater reliability (Kappa)
• Using deception obscure the true hypothesis
  (vodka)
  
• deliberately misinform the participants
  (debrief!!)
  
• (confederate) (vodka study)

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3. Control through subject selection assignment

• Random Sampling!!! Everyone has chance
  selections
  
• 
  do not affect each other
  
• only way to control for unknown factors
  (potential confounds)
  
• Potential confounds are evenly distributed!
• Subject Assignment random assignment!!!
• free random assignment (use random number
  table)
  
• matched random assignment (age, weight)

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Unbiased sample
Table of random or r generator
General Population Everyone..
Target population
Representative sample (n)
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Control through subject selection assignment

• Stratified random sampling
• Define exactly what target pop is based and
  match
  
• proportion in the population

General Population Everyone..
Target population
Representative sample (n)
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4. Control over experimenter design
? Simple Pretest-posttest design
? Pretest-posttest, control group design