1. Chapter 9 – Lecture 8

2. Some ways to control threats 1.General control procedures 2.Control over subject and experimenter effects 3.Control through participant selection and assignment 4.Control through specific experimental design

3. 1. General Control Procedures Control over research setting Lab ++internal validity --generalization Applied setting --internal validity ++generalization Natural environment In the lab Stanford Prison Experiment - the psychological effects of becoming a prisoner or prison guard. - set up a simulated a prison

4. basement of Stanford's Psychology Department building 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

5. Replication Pilot experiment Exact replication Response Measurement Focus on the DV: careful selection of the measurement make sure measure is validated (scale)…reliable (scale development)

6.  blind & double blind procedures Experimenter knows the hypothesis, subject assignment etc… 2. Control over Subject & Experimenter effect - motivation - knowledge - expectations Blind: research assistant “blind” to assignment into a group Double Blind: both RA & Subject do not know (drug studies/ light therapy)

7.  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)

8.  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) 3. Control through subject selection & assignment General Population Everyone.. Target population Representative sample (n) 2 1 3 Unbiased sample Table of random # or r# generator

9. Stratified random sampling:  Define exactly what target pop is based and match proportion in the population Control through subject selection & assignment General Population Everyone.. Target population Representative sample (n)

10.  Simple Pretest-posttest design  Pretest-posttest, control group design 4. Control over experimenter design