Psychology, Research, Independent Variable, Dependent Variable, Experimental, Correlation, Cause and Effect

1. Research in Psychology
 Is Empirical
(based off observation)
 Measures and Describes
( psychological constructs and operational definitions)
 Makes a Prediction
(formulates a hypothesis about the relationship
between 2 or more variables)
 Suggests an application
(understanding allows control over our environment)

2. Theories, Hypotheses, and Research
 Theories (from the specific to the general)
 Hypotheses (from the general to the specific)
 Research ( a term for the multiple ways a
hypothesis can be tested)

3. Steps in Scientific Research
1) Establish a testable hypothesis (operational
definition must be clear and precise)
2) Design the Study (how you will test and measure
the variables of interest)
3) Collect the Data (Could be though direct
observation, questionnaires, or behavioral tests)
4) Analyze Data and Suggest an Application
(statistical analysis and relevance of research)
5) Report the findings (writing a research report
and journal submission)

4. Experimental Research
 Establishes Cause and Effect
 Independent Variable (IV): is manipulated
 Dependent Variable (DV): is measured
 Experimental Group : receives the (IV)
 Control Group: receives nothing or placebo

5. Experimental Research
 Population (random selection)
 Sample (random assignment)

•
•
•
•
Extraneous Variables: are controlled
Selection bias (random selection)
Assignment bias (random assignment)
Experimenter bias (double-blind study)
Novelty effects (field study)
 Confounding Variables: have an effect on the (DV)

6. Alleviation of Depression = Dependent Variable
Between-Subjects Experimental Design
Experimental Group
Control Group
Receives the IV (antidepressant)
Receives nothing (placebo)

7. Identify the (IV) and the (DV)
• A researcher is conducting a study to see if room
temperature influences learning.
• Of 100 individuals with obsessive-compulsive
disorder (OCD), 50 receive 8 weeks of an
experimental drug for OCD, while 50 are placed
on a waiting list for 8 weeks. At the end of the 8
weeks, all 100 individuals are given psychological
tests to assess their level of OCD.

8. Variations in Experimental Designs
Within-Subjects Experimental Design
 Some experimental designs do not compare
groups. (no random assignment)
All members of the sample participate in both
control and experimental conditions.
 A researcher is evaluating the effects of a
study skills class on the GPA scores of college
Freshman.

9. Variations in Experimental Designs
Single-Subject Experimental Design
Researchers may choose to experiment with a
single Participant. (no random selection or
random assignment)

10. Statistical Analysis
 The Null Hypothesis (accept or reject)
 Type I Error: rejecting a true null hypothesis
 Type II Error: accepting a false null hypothesis
 The Alpha Level: the probability of chance occurrence
• Low Alpha (.01) increased risk of type II error
• High Alpha (.05) increased risk of type I error

11. Advantages and Disadvantages of Experimental
Research
Advantages
 It is the only form of
research that can establish
cause and effect.
 Experiments allow the
researcher precise control
over variables.
Disadvantages
 Experiments are often
artificial.
 Some experiments cannot
be conducted due to ethical
concerns.

12. Correlational Research
 A Non-experimental form a research that
shows a directional relationship between
variables.
 Correlational Coefficient (numerical value
that determines the strength of a relationship
between variables between -1 and +1)

13. Positive Correlation
 High scores on X are related to high scores on Y, and low scores on X are
related to low scores on Y.
X
Y
Years Smoking
Risk of Cancer
X
Y
Years Smoking
Risk of Cancer

14. Negative Correlation
 High scores on X are related to low scores on Y, and low scores on X are
related to high scores on Y.
Y
x
Amount of
cocaine
hours of
sleep
x
Amount of
cocaine
hours of
sleep

15. No Correlation
A correlation coefficient of (0) indicates there
is no relationship between variables.

16. Correlational Coefficient
Negative Correlation
Positive Correlation
-1_______________________0______________________+1
Strength of Relationship
Increasing
Increasing

17. Advantages and Disadvantages of Correlational
Research
Advantages
 It allows researchers to
study variables that would
be unethical to manipulate.
 Researchers can study
variables as they exist
naturally.
Disadvantages
 Correlations are not able to
show cause and effect. (no
manipulation of the (IV)
 They provide little control
over extraneous variables.
 The direction of the
relationship is unclear.