3. 98% Certainty
1. The area of the US in square miles?
2. The population of Afghanistan in 2001?
3. American battle deaths in Spanish-
American War?
4. GM advertising budget in 1999?
5. Female officers in US Army in 2000?
4. 98% Certainty
1. Area of US: 3.6 million sq. miles
2. Afghan population: 26.8 million
3. Battle deaths: 385
4. GM advertising: $2.9 billion
5. Female officers: 9.953
5. I. The Need for Psychological Science
A. Limits of intuition and common sense
1. Hindsight bias
2. Overconfidence
6. I. The Need for Psychological Science
A. Limits of intuition and common sense
B. Scientific attitude
C. Scientific method
1. Theory & hypothesis
2. Operational definitions
3. Replication
4. Goals:
9. 72% interested in “plants & trees”
39% interested in “botany”
62% whites agree “problems faced by blacks
brought on by blacks themselves” (white
interviewer)
46% whites agree with black interviewer
A majority oppose an amendment
“prohibiting abortions”
A majority support “protecting the life of an
unborn child”
10. 1. Is the Mississippi River longer or
shorter than 500 miles?
2. How many miles long is it?
11. 1. Is the Mississippi River longer or
shorter than 3000 miles?
2. How many miles long is it?
12. II. Description
A. Case studies
B. Surveys (questionnaires & interviews)
1. Wording effects
2. Samples & populations
a. False consensus & other biases
b. Random & representative
techinques
13.
14. II. Description
A. Case studies
B. Surveys (questionnaires & interviews)
C. Naturalistic observation & observer
effects
19. III. Correlation
A. Positive & negative
B. Scatterplots
C. Correlation coefficient (r)
D. Causation v. predictive value
Correlation between TV watching & GPA
20.
21.
22.
23. III. Correlation
A. Positive & negative
B. Scatterplots
C. Correlation coefficient (r)
D. Causation v. predictive value
E. Illusory correlation
F. Order in random events
25. IV. Experimentation
Purpose of an expt:
General hypothesis: food effects learning
Specific (operationalized) hypothesis:
students who eat an oatmeal raisin cookie
before class each day will have higher
average scores on the semester final than
students who don’t eat a cookie.
26. Eating cookies before class each day will
lead to higher average scores.
Variables:
Independent (IV)
Controlled by experimenter
The “cause” variable
Dependent (DV)
Predicted by experimenter
The “effect” variable
27. Eating cookies before class each day
will lead to higher average scores.
What if kids get cookies and A’s?
Groups (conditions): to establish different
levels of the IV
Experimental group
Exposed to IV
Get cookie
Control group
Not exposed to IV
No cookie
28. Eating cookies before class each day
will lead to higher average scores.
Confounding
IV DV
Variables
Expt. Gp. Cookie 95% Environmental
Cntrl. Gp. No Cookie 82% Expectations
Individual
differences
29. Random Sampling
To select participants from population
Allows you generalize results
Random Assignment
To divide participants into groups
Controls confounding variables
30. Eating cookies before class each day
will lead to higher average scores.
IV DV
Expt. Gp. Cookie 95%
Cntrl. Gp. No Cookie 82%
85%
93%
32. Replication
Non-replicated results are preliminary.
Linus Pauling (1970). Vitamin C prevents
colds.
IV DV
Expt. Gp. Vit C Expt. Gp.
45%
Cntrl. Gp. Placebo Fewer colds
33. Experimental Design Terms
• Hypothesis
• Operational definitions
• Participant selection
• IV & DV
• Experimental & control groups
• Confounding variables
• Random assignment
• Placebo control
• Double blind procedure
• Statistical significance (p value)
• Replication
39. Histogram
50
Percentage of students
40
30
20
10
0
A B C D
Grades
40. Frequency Polygon
50
Percentage of students
40
30
20
10
0
A B C D
Grades
41. V. Statistical Reasoning
A. Describing data
B. Measures of central tendency
Mode=most common=4
4 Mean=arithmetic average=20/5=4
3
5 Median=middle score=4
4
4
42. Central Tendency
1968 TOPPS Baseball Cards
Nolan Ryan $1500 Elston Howard $2.25
Billy Williams $8 Jim Bouton $2
Luis Aparicio $5 Rocky Colavito $2
Harmon Killebrew $5 Boog Powell $2
Orlando Cepeda $3.50 Luis Tiant $2
Maury Wills $3.50 Tim McCarver $1.75
Jim Bunning $3 Tug McGraw $1.75
Tony Conigliaro $3 Joe Torre $1.5
Tony Oliva $3 Rusty Staub $1.25
Lou Pinella $3 Curt Flood $1
Mickey Lolich $2.50
With Ryan: Without Ryan:
Median=$2.50 Median=$2.38
Mean=$74.14 Mean=$2.85
43.
44. V. Statistical Reasoning
A. Describing data
B. Measures of central tendency
C. Measures of variation
1. Range
2. Variance & standard deviation
45. Standard Deviation
Punt Deviation Deviation
Distance from Mean Squared
36 -4 16 std. dev.=
38 -2 4
variance=
41 +1 1
45 +5 25
11.5=3.4 yds
Mean= 46
160/4=
40 yds 46/4=11.5=
variance
46. V. Statistical Reasoning
A. Describing data
B. Measures of central tendency
C. Measures of variation
D. Characteristics of the normal curve
47. V. Statistical Reasoning
A. Describing data
B. Measures of central tendency
C. Measures of variation
D. Characteristics of the normal curve
E. Inference
1. Does the sample represent the pop.?
a. Non-biased sample-good
b. Low variability-good
c. Larger samples-good
48. V. Statistical Reasoning
E. Inference
1. Does the sample represent the pop.?
2. Are differences between groups
statistically significant?
a. Big differences-good
b. Low variability-good
c. Big groups-good
50. VI. FAQs
A. Can lab expts illuminate real life?
B. Does behavior depend on one’s culture?
C. Does behavior vary with gender?
D. Why do psychologists study animals?
E. Is it ethical to experiment on animals?
F. Is it ethical to experiment on people?
G. Is psychology free of value judgments?
H. Is psychology potentially dangerous?
51. VI. FAQs
F. Is it ethical to experiment on people?
Yes, if the APA’s ethical guidelines are
followed.
1. Informed consent
2. Protection from harm
3. Confidentiality
4. Debriefing
52. How should participants be
chosen?
• Good answers use and make clear your
understanding of the terms “sample” and
“population.”
• Good answers explain how to draw a
random sample.
• Ex. “All the assembly line workers for a
company could be the population. I would
draw a random sample of 40 of them by
picking names from a hat.”
53. Create operationalized hypothesis
• Good answers make an educated guess
(“Workers who are complimented will work
harder”)
• Good answers develop specific, measurable
ways to define compliments and hard work.
• Ex. “10 compliments will be given at 4 specific
times.” “Supervisors will give compliments from
a pre-developed list.” “Hard work will be
measured by using the number of items
produced each hour.”
54. Identify IV & DV
• IV=compliments
• DV=work effort
• Do not propose a direction when stating
the variable (“the DV is an increase in
work.”)
• People are never the variables (“the IV is
the people who get complimented.”)
55. Describe the groups
• Experimental group gets compliments.
• Control group doesn’t get compliments.
• Use the terms!
56. Confounding variables
• Do not confuse random assignment with
random sampling.
• Be reasonable!!!
• “The company policy will be to have
people sleep in a hotel with no TV or
radio.”
• “I will provide a seminar on the importance
of sleep.”
• “All workers must be paid the same.”
