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Chapter 2
Psychology’s Scientific Method
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2. © 2011 The McGraw-Hill Companies, Inc.
Chapter Preview
Psychology’s Scientific Method
Types of Psychological Research
Research Samples and Settings
Analyzing and Interpreting Data
Conducting Ethical Research
Thinking Critically About Research
Scientific Method and Health and Wellness
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3. Scientific Method
Science is a method. It’s not what you study, but how you study it.
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4. © 2011 The McGraw-Hill Companies, Inc.
Scientific Method
observe some phenomenon
formulate hypothesis and predictions
test through empirical research
draw conclusions
evaluate the theory
IM: Activity Handout 2.1: What is the Operational Definition?
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5. Scientific Method: Observe
Step 1
Observe some phenomenon
curiosity
variables
theory
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6. Scientific Method: Hypothesize
Step 2
Formulate hypotheses and predictions
testable prediction
derived from theory
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7. Scientific Method: Research
Step 3
Test through empirical research
operational definition of variables
analyze data using statistical procedures
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8. Scientific Method: Conclusions
Step 4
Draw conclusions
replication of results → reliability
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9. Scientific Method: Evaluate
Step 5
Evaluate the theory
change the theory?
peer review and publication
meta-analysis
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Descriptive Research
Goal: Describing a phenomenon
observation
surveys and interviews
case studies
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Descriptive Research
Descriptive research does not answer questions about how and why things are the way they are.
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12. Correlational Research
Goal: Identify relationships
correlation coefficient: r
-1.00 ≤ r ≤ 1.00
strength of relationship: magnitude
direction of relationship: + / -
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13. Correlation Coefficients
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Scatter Plots
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15. Correlational Research
Positive Correlations
factors vary in same direction
↑ and ↑ … or … ↓ and ↓
Negative Correlations
factors vary in opposite direction
↑ and ↓ … or … ↑ and ↓
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16. Correlation and Causation
correlation does not equal causation
third variable problem
longitudinal design
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17. Experimental Research
Goal: Determine causation
random assignment
independent variable(s) – manipulation
dependent variable(s) – measurement
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18. Experimental Research
Experimental Group
independent variable is manipulated
Control Group
treated equally, except no manipulation of independent variable
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Validity
External Validity
representative of real world issues?
do results generalize to the real world?
Internal Validity
are dependent variable changes the result of independent variable manipulation?
bias? logical errors?
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Bias and Expectations
experimenter bias
demand characteristics
research participant bias
placebo effect
double-blind experiment
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Research Sample
Population
entire group about whom conclusion drawn
Sample
portion of population actually observed
Representative Sample
characteristics similar to population
opposite of “biased sample”
Random Sample
equal chance of being selected
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22. © 2011 The McGraw-Hill Companies, Inc.
Research Settings
“Artificial” world – laboratory setting
controlled setting
Real world - natural setting
naturalistic observation
What are the advantages and disadvantages
of each setting?
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23. Analyzing and Interpreting Data
Statistics
mathematical methods used to report data
Descriptive Statistics
describe and summarize data
Inferential Statistics
draw conclusions about data
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24. Descriptive Statistics
Measures of Central Tendency
mean
median
mode
Measures of Dispersion
range
standard deviation
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25. Inferential Statistics
does data confirm the hypothesis?
statistical significance
α = 0.05 (confidence level)
bridge between sample and population
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26. © 2011 The McGraw-Hill Companies, Inc.
Research Ethics
research participants have rights
Institutional Review Board (IRB)
APA Guidelines
informed consent
confidentiality
debriefing
deception
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27. Animal Research in Psychology
animal research has benefited humans
used by 5% of researchers
rats and mice used 90% of time
standards of care in animal research
housing
feeding
psychological and physical well being
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28. A Wise Consumer…is skeptical yet open-minded!
Cautions
exercise caution in applying group trends to individual experience
avoid overgeneralizing results
look for converging evidence
question causal inferences
consider the source
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