Chapter 2
Psychology’s Scientific Method
© 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
© 2011 The McGraw-Hill Companies, Inc.
Scientific Method
Science is a method.
It’s not what you study,
but how you study it.
© 2011 The McGraw-Hill Companies, Inc.
Scientific Method
1.
2.
3.
4.
5.
observe some phenomenon
formulate hypothesis and predictions
test through empirical research
draw conclusions
evaluate the theory
© 2011 The McGraw-Hill Companies, Inc.
Scientific Method: Observe
Step 1
Observe some phenomenon
 curiosity
 variables
 theory
© 2011 The McGraw-Hill Companies, Inc.
Scientific Method: Hypothesize
Step 2
Formulate hypotheses and predictions

testable prediction

derived from theory
© 2011 The McGraw-Hill Companies, Inc.
Scientific Method: Research
Step 3
Test through empirical research

operational definition of variables

analyze data using statistical procedures
© 2011 The McGraw-Hill Companies, Inc.
Scientific Method: Conclusions
Step 4
Draw conclusions

replication of results → reliability
© 2011 The McGraw-Hill Companies, Inc.
Scientific Method: Evaluate
Step 5
Evaluate the theory

change the theory?

peer review and publication

meta-analysis
© 2011 The McGraw-Hill Companies, Inc.
Descriptive Research
Goal: Describing a phenomenon
observation
 surveys and interviews
 case studies

© 2011 The McGraw-Hill Companies, Inc.
Descriptive Research
Descriptive research does
not answer questions about
how and why things are the
way they are.
© 2011 The McGraw-Hill Companies, Inc.
Correlational Research
Goal: Identify relationships

correlation coefficient: r
-1.00 ≤ r ≤ 1.00

strength of relationship: magnitude

direction of relationship: + / © 2011 The McGraw-Hill Companies, Inc.
Correlation Coefficients
© 2011 The McGraw-Hill Companies, Inc.
Scatter Plots
© 2011 The McGraw-Hill Companies, Inc.
Correlational Research
Positive Correlations
 factors vary in same direction
 ↑ and ↑ … or … ↓ and ↓
Negative Correlations
 factors vary in opposite direction
 ↑ and ↓ … or … ↑ and ↓
© 2011 The McGraw-Hill Companies, Inc.
Correlation and Causation

correlation does not equal causation

third variable problem

longitudinal design
© 2011 The McGraw-Hill Companies, Inc.
Experimental Research
Goal: Determine causation

random assignment

independent variable(s) – manipulation

dependent variable(s) – measurement
© 2011 The McGraw-Hill Companies, Inc.
Experimental Research
Experimental Group
 independent variable is manipulated
Control Group
 treated equally, except no
manipulation of independent variable
© 2011 The McGraw-Hill Companies, Inc.
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?
© 2011 The McGraw-Hill Companies, Inc.
Bias and Expectations

experimenter bias

demand characteristics

research participant bias

placebo effect

double-blind experiment
© 2011 The McGraw-Hill Companies, Inc.
Example of Experimental Research –
Self Esteem
Baumeister’s research findings:
“high self esteem leads to aggression”
Donnellan & Trzesniewski’s research findings:
“low self esteem leads to aggression”
What accounts for these different findings?
 lab-only aggression?
 type of self esteem?
© 2011 The McGraw-Hill Companies, Inc.
Applying Different Research Methods
to Same Phenomenon
Example: Election of President Barack Obama
Possible Research Methods
observation
survey and interview
case studies
correlational research
experimental research
© 2011 The McGraw-Hill Companies, Inc.
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
© 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?
© 2011 The McGraw-Hill Companies, Inc.
Analyzing and Interpreting Data
Statistics

mathematical methods used to report data
Descriptive Statistics

describe and summarize data
Inferential Statistics

draw conclusions about data
© 2011 The McGraw-Hill Companies, Inc.
Descriptive Statistics
Measures of Central Tendency



mean
median
mode
Measures of Dispersion


range
standard deviation
© 2011 The McGraw-Hill Companies, Inc.
Inferential Statistics

does data confirm the hypothesis?

statistical significance

α = 0.05 (confidence level)

bridge between sample and population
© 2011 The McGraw-Hill Companies, Inc.
Research Ethics



research participants have rights
Institutional Review Board (IRB)
APA Guidelines
informed consent
confidentiality
debriefing
deception
© 2011 The McGraw-Hill Companies, Inc.
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
© 2011 The McGraw-Hill Companies, Inc.
Reality TV – Ethical Issues

informed consent?

deception?

psychological and/or physical risk?

is the behavior real?
© 2011 The McGraw-Hill Companies, Inc.
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
© 2011 The McGraw-Hill Companies, Inc.
Expressive Writing & Health
Results of study on suicide v. accidental death
 different survivor health
 different survivor rate of talking about the loss
Results lead to study on writing
 those assigned to write about a trauma
experienced better physical health
© 2011 The McGraw-Hill Companies, Inc.
Chapter Summary





Explain what makes psychology a science.
Discuss common research settings and the main
types of research that are used in psychology.
Distinguish between descriptive statistics and
inferential statistics.
Discuss some challenges that involve ethics, bias,
and information.
Discuss scientific studies on the effect of writing
about ones trauma.
© 2011 The McGraw-Hill Companies, Inc.
Chapter Summary
Steps of the Scientific Method
 observe, hypothesize, research,
conclude, evaluate
Research Methods and Settings
 descriptive, correlational, and
experimental studies conducted in
natural settings or the lab
© 2011 The McGraw-Hill Companies, Inc.
Chapter Summary
Data Analysis and Interpretation
 descriptive and inferential statistics
Challenges: Research Ethics and Bias
 APA guidelines and the IRB
Expressive Writing and Health and Wellness
 benefits of writing about trauma
© 2011 The McGraw-Hill Companies, Inc.