1. Research Methods
3. Experimental Research

2. Experimental research
Experiment: Manipulation of one variable under controlled conditions so that resulting changes in another variable can be observed.
Detection of cause-and-effect relationships
How does X affect Y?
X = Independent Variable
Y = Dependent Variable
Independent variable (IV): variable that is manipulated
Dependent variable (DV): variable that is measured

3. EXPERIMENTAL RESEARCH
Population: entire group
Sample: subset of the population
Random Sampling or Random Selection: Each member of a population has an equal chance of being selected.
Unbiased; objective
Sampling bias: Occurs when a sample is NOT representative of the population.
If the sample is biased, the results are NOT valid

4. Experimental research
Experimental Group: receives special treatment (IV)
Control Group: does not receive special treatment (IV)
Manipulate IV for one group only
Resulting differences in the two groups must be due to the IV
Random Assignment: assignment of participants to groups by chance
Reduces extraneous variables
Reduces bias

6. Experimental research
Extraneous Variable: Any variables other than the independent variable that may influence the dependent variable in a study.
1. Situational
2. Participant
3. Experimental
Confounding of Variables: When the effects of an extraneous variable are difficult to separate from the effects of the independent variable.
Influences the dependent variable

7. Experimental research
Experimenter Bias: experimenter’s expectation influence outcome
Participant Bias: participant's expectation influence outcome
Placebo Effect: Occurs when a participant’s expectations produce change even though they receive a “fake” treatment.
Hawthorne Effect: The tendency of individuals to perform better simply because of being singled out and made to feel important.

8. Experimental research
Double-blind: BOTH the participants and the experimenters remain unaware of which participants are in the experimental group and control group.
This eliminates both participant bias
and experimenter bias
Used for drug trials
OBJECTIVE 13| Explain why random assignment and double-blind procedure build confidence in research findings.
Psychology 7e in Modules

9. Experimental research
EXPERIMENTAL VARIATIONS
Expose a single group to two different conditions
-Reduces extraneous variables
Manipulate more than one independent variable
- Allows study of interactions between variables
Measure more than one dependent variable
- Obtains a more complete picture of effect of the independent variable

11. Experimental research
Description: Manipulation of one variable under controlled conditions so that the resulting changes in another variable can be observed.
Advantages
Disadvantages
Shows cause and effect relationship!!!
Manipulation of variables
Precise Control
Generalizability
Artificial situations
Costly
Ethical issues