Psych 104 unit 2c

Experimental designs

• Permit scientists to make cause-effect inferences

• Manipulate variables to see if it produces differences in behaviour

Experiment

• Random assigment

• Manipulation of independent variable

• Control over extraneous variables

• Measure depending variable and compare

Between subject design

The control and experimental group are made up of different participants

Within subject design

• Each participant acts as their own control

• Measures counterbalanced

External validity

Degree to which findings can be generalized to the real world

Internal validity

Degree to which experiment can support clear casual conclusions

The placebo effect

• Improvement resulting from the expectation of improvement

• Controlled by “dummy treatment”

• Can act as a confounding variable if no placebo is given

Single blind

Participants don’t know which treatment they get, but researchers do

Double blind

• Participants and researchers don’t know which treatment they get

• Protects against bias & placebo effect

Milgram experience

• Was done to find put why people obeyed the Nazis in germany

• “Teachers” (research participants) administered shocks to “students” upon the researchers request

• Was criticized for being unethical

Ethical guidelines for human research

• Research ethics boards or review boards

• At least one at every research institution

Canadian code of ethics for psychologists

• Protect and promote subject welfare

• Avoid causing harm

• Potential benefit must be greater than risk

• Provide informed consent

• Ensure privacy

Informed consent

• Participants told they can withdraw from the study without any penalty

• Participants can ask questions

• Deception is only justified if the study couldn’t have been preformed without deception (eg: Milgram), allowed to withdraw (which is why Milgram was unethical)

• Does not negatively affect the rights of the participants

Debriefing

• Told true purpose pf study at the end of the experiment, especially necessary if deception was used

• Non-technical explanation of hypothesis

• All participants entitled

Guidelines for humane treatment of animals

• Canadian council of animal care

• All research reviewed by animal care and use comittees

• Weigh the potential benefits against the cost of animal suffering

• Animals not subject to stress or pain unless no alternative possible