1. BHV 390 Experiments

2. Pros about Experiments Experimental research is the best explanatory design. It is the best design to test causal relationships Experiments attempt to eliminate all “lurking variables” by removing the participants from real life as much as possible

3. Cons about Experiments Mundane realism – experiments are done in controlled environments that are not like real life Hawthorne effect - participants may respond differently when they know they are being observed Placebo effect – participants in who are given a mock stimulus may react as if they are being affected by the stimulus because they expect to be affected

4. Components of an Experiment Independent variable – the variable that is believed to cause change in other variables Dependent variable – the variable that is changed by the independent variable Sample – the whole group chosen to participate in the study Pretest – measuring the dependent variable before the experiment begins Post test – measuring the dependent variable after the experimental group has been exposed to the stimulus Experimental group – the group that will receive the independent variable stimulus Control group – the group that will not receive the independent variable stimulus Stimulus, (also manipulation, intervention) – exposure of the experimental group to the independent variable

5. Creating Experimental and Control Groups Random Assignment uses probability sampling techniques to assign cases control and experimental groups Matching uses matched criteria to set up similar control and experimental groups Non-random assignment leaves doubt about whether the groups are equivalent

6. Classical Experiment 1. Choose an IV* 2. Choose a DV** 3. Choose a Sample 4. Divide the sample into experimental and control groups. 6. Pre-test the whole sample on the DV. 7. Present the IV stimulus to the experimental group. 8. Post-test both control and experimental groups on DV 9. Compare and analyse the two sets of DV measurements. * Independent Variable** Dependent Variable

7. Classical Experiment

8. Solomon Four-Group Design (Extra Step to eliminate pre test bias) 1.Choose an IV 2.Choose a DV 3.Choose a Sample 4. Divide the sample into four groups. 5. Pre test groups 1 and 2 on the DV. 6. Present the IV stimulus to groups 1 and 3. 7. Post test groups 1 through 4 on the DV 8. Compare and analyse the four sets of results.

9. Solomon Four Group Experiment

10. One Shot Case Study (No control group, no pretest) 1.Choose an IV 2.Choose a DV 3.Choose a Sample 4.Present the IV stimulus to the whole sample. 5.Post test the whole sample. 6.Analyze and draw conclusions from the whole sample.

11. One Shot Case Study

12. One Group Comparison (No control group) 1.Choose an IV 2.Choose a DV 3.Choose a Sample 4. Pretest the sample 5. Present the IV stimulus to the whole sample. 6. Post test the whole sample 7. Analyze and draw conclusions from the whole sample.

13. One Group Comparison

14. Static Group Comparison (No pre test) 1.Choose an IV 2.Choose a DV 3.Choose a Sample 4.Divide the sample into experimental and control groups. 5.Present the IV stimulus to the experimental group. 6.Post test both experimental and control groups. 7.Compare and analyse the two sets of results.

15. Static Group Comparison

16. Double Blind Experiment (Conceals experimental group) 1. Choose an IV 2. Choose a DV 3. Choose a Sample 4. Divide the sample into experimental and control groups. 5. Conceal experimental and control group identity from experimenters. 6.Pretest the whole sample. 7.Present the IV stimulus to the experimental group. 8.Post test both experimental and control groups. 9.Compare and analyse the two sets of results.

17. Double Blind Experiment

18. Natural Experiment (No control over experimental stimulus) 1. Choose an IV 2. Choose a DV 3.Locate a convenient sample that is due to be exposed to a naturally occurring stimulus (IV) (experimental group) 4.Locate a convenient sample that is NOT due to be exposed to that naturally occurring stimulus (IV) (control group) 5. Collect data on the DV from both populations (pre test). 6. Wait for the naturally occurring IV stimulus to affect the experimental group. 7. Collect data on your DV from both populations (post test). 8. Compare and analyse the two sets of results.

19. Natural Experiment

20. Study Guide Control GroupClassical experiment Experimental GroupSolomon four group experiment Independent variableOne shot case study Dependent variableOne group comparison SampleStatic group comparison Stimulus/manipulationDouble blind experiment PretestNatural experiment Posttest Mundane realism Hawthorne effect Placebo effect Random assignment Matching Non-random assignment