2. Psychological Research Methods
Learning Target: Compare and contrast research methods (case studies, survey, naturalistic observation, correlational studies)

3. Modern psychology aims to be an empirical science, which means that assumptions are supported by scientific evidence
Psychologists use scientific method to test hypotheses & develop theories

4. Operational Definition
Specifies how a variable will be defined and measured
If my variable is memory, how will I define and measure it?
Operational Definition: A person has a good memory if they can memorize a list of 30 random words in two minutes or less and then write them down on a sheet of paper.

5. Population: the group that is targeted for the study
Sample: segment of the population to be studied
Random sample: each member of a population has an equal chance of being selected to participate
Stratified sample: identified subgroups in the population are represented proportionately in the sample

6. Psychologists then draw conclusions based on their observations and findings
When observations do not support the hypothesis, a psychologist may modify the theory from which the question originated
Replicate: repeat a study to ensure that data is accurate (if get different results, study is invalid)
Generalize: apply results to population as a whole

7. Bias in Research
Volunteer bias: people who offer or volunteer to participate in research studies differ from those who do not, therefore this skews the findings
Social desirability bias: many people tend to tell the interviewer what they think the interviewer wants to hear and not what they really think

8. Validity & Reliability
Validity: when a study measures what the researchers set out to measure
Reliability: when results of a study be replicated, are consistent when repeated

9. Observational Methods: Case Study
Case study: examine one individual or small group
Pros:
- Detailed & specific info
- Good in rare cases
Cons:
- No generalization (unique case)
- Cannot test theories

10. Observational Methods: Survey
Survey: a large sample of people answer questions about their attitudes or behavior
Pros:
- More info, less time, less $
- Better to generalize
Cons:
- Social Desirability Bias
- Poor wording
- Interviews are less honest or candid – Bathroom study (95% v. 67%)
- Inaccurate recall

11. Observational Methods: Naturalistic Observation
Naturalistic Observation: subjects are observed in natural environment
- No attempt to influence or control
Pros:
- behavior is natural & spontaneous
Cons:
- Wait for behaviors to occur
- Observer bias
Jane Goodall

12. Correlational Method Sir Francis Galton (1822-1911)
Correlation = degree of relationship between variables (r)
“Correlation does not prove causation”

13. Example: Data  Is income related to years of school?
Years of College
Income at Age 25 ($)
20,500  .75
33,000 
30,000 
23,500 
32,000  3.5
27,500  3
24,000  2.15
26,000 

14. Fig. 1.9 The relationship between years of college completed and personal income (hypothetical data).

15. Positive Correlation
As one variable increases, the other variable also increases (& vice versa)
Values between and +1.00
Among college students, those with higher SAT scores also have higher grades.
As people’s happiness level increases, so does their helpfulness.

16. Negative Correlation
As one variable decreases, the other variable increases (or vice versa)
Values between and -0.01
People who have more years of education tend to have fewer years in jail.
Among babies, those who are held more tend to cry less.

17. No Correlation Value of 0 – neither positive or negative
No linear relationship
For example, hours of sleep and number of stars in the sky

18. Fig. 1.7 The correlation coefficient tells how strongly two measures are related. These graphs show a range of relationships between two measures, A and B. If a correlation is negative, increases in one measure are associated with decreases in the other. (As B gets larger, A gets smaller.) In a positive correlation, increases in one measure are associated with increases in the other. (As B gets larger, A gets larger.) The center-left graph (“medium negative relationship”) might result from comparing anxiety level (B) with test scores (A): Higher anxiety is associated with lower scores. The center graph (“no relationship”) would result from plotting a person’s shoe size (B) and his or her IQ (A). The center-right graph (“medium positive relationship”) could be a plot of grades in high school (B) and grades in college (A) for a group of students: Higher grades in high school are associated with higher grades in college.

19. Correlations Pros: Cons: Importance of sample size!
Can make predictions (but no cause/effect)
Cons:
No causation
Importance of sample size!
Possibility of 3rd variable
Illusory correlations (“it always rains after you wash your car”)

20. Correlation Does NOT Prove Causation
“People who floss their teeth more often live longer.”
Could there be another reason why people who regularly floss their teeth live longer?
People who take care of their teeth probably take care of themselves in other ways too (exercise, proper diet, don’t smoke, etc.)
“The number of drownings in the U.S. rises and falls during the year, along with the amount of ice cream sold each month.”
Third variable (time of year) – summer – more likely to eat ice cream, swim in pools/lakes

21. Illusory Correlations: Homer Simpson
Springfield invests millions of dollars in a “Bear Patrol” after a single bear was spotted
Homer tells Lisa how well the patrol is working – “not a bear in sight”
Lisa challenges Homer’s conclusion:
Lisa: “By your logic, I could claim this rock keeps tigers away”
Homer: “How does it work?”
Lisa: “I don’t see any tigers around, do you?”
Homer: “Lisa, I want to buy your rock”

22. Experimental Method
Researcher manipulates one/more variable(s) to observe the effect on another variable
Control all conditions except for one or more variables
Independent Variable: variable manipulated by experimenter
Dependent Variable: variable which changes due to I.V. (the effect)

23. Experimental Method
Experimental group: group of participants which receives treatment or IV
Control group: group which not receive treatment while all other variables are held constant
Randomly assign participants to experimental or control group
Placebo: fake treatment (i.e. sugar pill)
Experiments are the only research method that can prove cause & effect

24. Fig Elements of a simple psychological experiment to assess the effects of music during study on test scores.

25. Example
College students’ memory for German vocabulary words is tested after a normal night’s sleep or a night of no sleep
“If students get more sleep, then they will remember more German vocab”
IV = sleep
DV = memory of vocab
Control group = normal night’s sleep
Experimental group = no sleep

26. Experimental Method
Blind study: subjects are unaware if assigned to experimental or control group
Double-blind study: neither subjects nor experimenters know which group is control or experimental

27. Longitudinal v. Cross-sectional Studies
Longitudinal – same participants over long period of time
i.e. studying effects of early childhood literacy program on later academic success
Cross-sectional – studies participants at one time
i.e. effect of a vitamin on memory recall