1. Scientific Methods
Chapter 2
Psychology 301

2. Basic Steps for Conducting Scientific Research
Step 1: Formulate a hypothesis 1.
Step 4:
Report the results
Step 2:
Design a study
Step 3: Collect & analyze data

3. The Scientific Process
Theory
Revise Theory
Hypotheses
Empirical Tests
Replicate
Not Supported
Supported
Confidence in theory decreases
Confidence in theory increases
Discard Theory

4. Types of psychological research
Experimental Research
Experiments
Descriptive/Correlational Research
Surveys
Observation
Naturalistic
Contrived
Case Studies

5. Experiments
Experiments - Do changes in one variable (X) cause changes in another variable (Y)?
Independent Variable (X)
condition or event that is manipulated by experimenter
Dependent Variable (Y)
variable that is affected (hopefully) by manipulating independent variable
Extraneous Variable(s)
any variable other than independent variable that may influence dependent variable

6. Example
A study was conducted to examine the effects of temperature on aggression. Participants were randomly assigned to one of three conditions (low [70o-72o], moderate [80o-82o], or a high [90o-92o] temperature room).
While in the room an assistant irritates the participants.
Participants were later given a chance to “evaluate” the assistant and told that low ratings would cause the assistant to be fired.

7. Research Methods

8. Research Methods Confounding of Variables
occurs when independent and extraneous variables are linked together
makes it impossible to tell which variable affected dependent variable

9. Research Methods Minimize confounding with consistent procedures
Minimize confounding with random assignment
participants have an equal chance of being assigned to any group or condition in the study.
the goal of random assignment is to equally distribute potential extraneous variables in each group.

10. Variations in experimental design
Use 1 group of participants who act as their own control group (e.g., expose each participant to each temperature)
Manipulate more than 1 independent variable at a time (temperature & humidity)
Measure more than 1 dependent variable at a time (aggression & helping)

11. Pros and Cons Advantages of Experimental Research
Allows conclusions about cause & effect relationships between variables
Disadvantages of Experimental Research
Experimental conditions are artificial
do results “generalize” to the real world?
Some questions can’t be tested in an experiment

12. Correlation/Descriptive Research
Advantages
Study phenomena that can’t be studied in a lab
riots
effects of supervisor behavior on employees
effects of job loss on couples’ relationship quality
effects of smoking on physical health
Very realistic
results can be generalized to other settings
Disadvantages
less control over extraneous variables
difficult to measure behavior as precisely (compared to lab experiments)
cannot demonstrate cause and effect relationships

13. Correlation
The extent to which one variable can be understood on the basis of another
Two properties of correlation coefficient
direction (positive or negative)
magnitude (strength of the relationship)

14. Positive Correlation
r = .95

15. No Correlation
r = .00

16. Negative Correlation
High
r = -.95
Low
Low
High