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Chapter 9 Procedure for Conducting an

Experiment

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Institutional Review Boards (IRBs)

• All research involving human subjects must be approved by IRB. •Primary concern is the welfare of the participants.

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Research Protocol – detailed description of a study.

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Risk/Benefit analysis- IRB boards decision is final!

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External validity – to whom and in what circumstances do the results of the study apply. External validity is not a design issue. It is a questioned that needs to be addressed in interpreting and using the findings of the study.

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Animal Research in Medicine

External validity here depends on how good a Model the biological systems on the animal is of the human system.

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Behaviorist and the Rats: What’s up with that?

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Research Participants

Inclusion and Exclusion Criteria

Convenience Samples – use who is available!- General Psychology Research Pool.

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Convenience and Availability Samples

Volunteer Problem

Importance of Random Assignment withConvenience Samples.

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Problems using non-college Populations

Special Populations (Children, Prisoners, Elderly, mentally or psychologically impaired.

Permission must be granted from every possible legal stakeholder.

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Want to study theseKids? Who has to approve it?

School BoardSchool PrincipalTeacherParents (Active Informed Consent)Child (Assent)

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Internet Research

Social Psychology NetworkAmerican Psychological Association

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Power – probability of rejecting a false null hypothesis.

Probability of detecting a difference between conditions when one exists.We want high power in our study.Approx 0.8

What does Power of 0.8 mean?

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Effect Size – Correlation between IV and DV.

Tells you how well you can predict the DV, if you know the participant’s IV condition.

e.g., If I know whether a person is male or female, how much does that improve my ability to predict their math ability.

Cohen’s (1992) Criteria.

Effect size or .10 is small, .30 is moderate and .50 is large.

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The larger the Effect Size is the more Power the study has.

• Very Powerful studies can find significant (not due to chance) effects that are very small.

• Studies with low power may be unable to detect even large effects of the IV

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Alpha Level: Chance we are willing to take of making a Type I error.

If we change alpha to .10, we would correctly accept a lot more comparisons as significant, but we will also greatly increase our chance of making a type one error.

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Sample Size, Power and Effect Size areRelated in such a way that if you know two of these values for a study, you can determine the third (from a chart) for a given alpha level.

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↑ Sample Size ↑ Power

↑ Effect Size ↑ Power

↑ Alpha ↑ Power

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Apparatus and /Instructions

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Procedure Instructions (Protocol)All subjects receive the same instructions with the exception of changes needed to manipulate the IV.

Scheduling Participants.Time of Day InteractionsRunning in Groups or Individually

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Pilot Studies- tests the procedure

- wording or the instructions- practice for the experimenter- run through for equipment and computer programs

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Debriefing (Post Experimental Interview)Functions 1) Ethical

- undo deception- undo stress

2) Educational Function

3) Post experimental Inquiry

4) Satisfaction