Experiments

1. Experiments Unit 2 – Mod 6

2. Experiment • controlled investigation used to show a cause-and-effect relationship • Experimenter purposely manipulates and controls selected variables

3. Variables • Independent Variable (IV) • Factor that is manipulated or controlled by the experimenter. • Dependent Variable (DV) • Factor that is measured by the experimenter • Affected by IV

4. Let’s Practice… • An experimenter wants to determine if playing violent video games increases the frequency of aggressive behavior in children. • An experimenter wants to determine the relationship between rehearsal/repetition of a list of definitions of difficult SAT vocabulary words and later recall of these definitions.

5. Operational Definition • Precise description of how the variable in a study will be manipulated and measured. • Needed for replication

6. Let’s Practice…. Is the statement Operationally Defined? a. Children who exercise are less likely to suffer from obesity. b. Dogs who overeat are more intelligent than those that do not. c. Instructors who smile ten times in their class have increased student participation. d. When sleeping two hours less than normal, people remember course materials less well. e. Moline High School is a better high school than Alleman High School.

7. Experiment • Experimental Group • Participants who get the treatment (independent variable) • Control Group • Participants who are exposed to all experimental conditions except the independent variable.

8. Confounding Variables • Differences between the experimental group and the control groups other than the IV • Have an unwanted influence on the outcome of an experiment • Example… • In a study measuring the impact of playing violent video games on the frequency of aggression in children • Confounding variables • Income level of kid’s parents • Incidence of child abuse

9. Problems with Experiments • Problems • Experimenter bias • Sample bias – research participants are not representative

10. Solutions to stop bias • Random assignment • Minimizes pre-existing differences between groups • Placebo • An inactive substance or fake treatment often used as a control technique in drug research

11. Solutions • Single-blind study • Procedure in which the subjects do not know whether they are in the experiment or control group • Double-blind study • Procedure in which neither the researcher nor the participant knows which group

12. Advantages • Identifies cause-and-effect • Distinguish between real and placebo effects • Control bias with double-blind • Allows for replication

13. Disadvantages • Artificial lab conditions that do not correspond to real-life situations • Can be compromised by confounding variables • Susceptible to researcher and participant biases • Raises ethical questions when subjects are deceived