Zimbardo

• Allocation of participants

  Participants were randomly allocated so researcher bias is reduced.
• Sample

  The sample is biased as they were all male and students and volunteered to be a part of the study.
• Validity

  Zimbardo was the prison superintendent and observed the behaviour.
• Observation

  Controlled observation so lacked ecological validity.
• Right to withdraw

  Zimbardo refused participants to leave the study.
• Protection from harm

  Participants went on hunger strike and became highly distressed.