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Psychology 7

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Title: Psychology 7


1
Psychology 7 Experimental Psychology
Complex Designs
Professor Gallagher and his controversial
technique of simultaneously confronting the fear
of heights, snakes, and the dark.
2
Mean 78
Approx. Curve 86-100 A 79-85 B 63-78 C 50-62 D lt
50 F
3
Factors and Levels
  • Factor is another term for independent variable
  • Experiment Randomly assign subjects to drink
    coffee or drink de-caf
  • One factor whether or not drink coffee
  • Levels refer to the different conditions within a
    factor
  • 2 levels in the coffee example regular coffee
    vs. de-caf
  • Experiment with a 3rd group drink caffeinated
    soda would have 3 levels but still one factor

4
One Factor Designs with gt 2 Levels
  • 2 basic reasons for having gt 2 levels
  • Need more than 2 to detect curvilinear or complex
    relationships between variables
  • May want multiple control groups/be interested in
    multiple conditions

.
.
.
1
2
3
Yerkes-Dodson Law
5
Bandura Study of Imitative Aggression
  • Children (3-5 yrs) assigned to 1 of 3 conditions
  • Observe aggressive adult beat up Bobo doll
  • Observe nonaggressive adult not beat up Bobo doll
  • No exposure to any adult model
  • Matched Pairs Design Children were enrolled in
    Stanford Universitys Nursery School
  • Rated by teachers for degree of aggressiveness
  • Matched for aggressiveness before being randomly
    assigned to conditions
  • Hypotheses (1) Kids exposed to aggressive
    models would perform more aggression than those
    in other 2 groups, (2) Exposure to nonaggressive
    model would inhibit aggression (prediction no
    exposure kids gt aggression than nonaggressive
    condition)

6
  • Dependent variable measured in a different room
    in the absence of the adult models
  • Prior to the test for imitation, however, all
    subjects were subjected to mild aggression
    arousal to insure that they were under some
    degree of instigation to aggression.
  • Experimenter brought kids into room with
    attractive toys and after letting them get
    engaged with them ( 2 min.), remarked that
    these were her very best toys, that she did not
    let just anyone play with them, and that she had
    decided to reserve these toys for the other
    children.
  • Modeling apparently doesnt work without this
    added instigation
  • Observers counted of aggressive acts in
    specific categories behind one-way mirror over 20
    minute interval

7
Results
Bandura, Ross, Ross (1961)
8
Factorial Designs
Factorial designs involve gt 1 independent
variable or factor All levels of each
independent variable are combined with all levels
of the other independent variables
Example Balanced Placebo Design Study
Factor 1 Level 1 Level 2 Factor 2 Level
1 Level 2
  • Alcohol expectations
  • Expect vodka
  • Expect tonic
  • Alcohol intake
  • Drank vodka
  • Drank tonic

9
Alcohol Study
Expectations
Alcohol
No alcohol
Tonic
Intake
Vodka
...a 2(rows) x 2 (columns) design
10
Multiplicative Notation
A 3 x 4 factorial design
2 Factors with 3 and 4 levels
12 cells total (3 x 4)
A 2 x 2 x 2 factorial design How many
factors? How many cells?
11
Alcohol Example
Expectations
Alcohol
No alcohol
Group 1 average
Group 3 average
Tonic
Group 2 average
Group 4 average
Intake
Vodka
Usually, averages are in the cells
12
Main Effects
  • Main effects are the effects of each independent
    variable considered separately
  • E.g., does actually drinking vodka produce higher
    levels of shock delivered to a learner than
    drinking tonic? (main effect of alcohol intake)
  • Main effects compare the effects of levels within
    a factor averaged across all levels of the other
    factors
  • The number of possible main effects is equal to
    the number of factors

13
Main Effects in Baseball
  • Right-handed (RH) vs. Left-handed (LH) batters
    face either a Right-handed (RH) or Left-Handed
    pitcher

A main effect looks at the effect of 1 factor
while ignoring the others
Pitcher
RH
LH
Main Effect of Handedness LH gt RH
RH
Batter
LH
14
Interaction Effects
  • When the effect of one independent variable
    depends on the level of another independent
    variable
  • Cannot fully understand the influence of one
    independent variable without reference to another
    independent variable

15
Interaction Effects in Baseball
  • External Validity Extent to which results of a
    study would be found with different participants
    or in a different setting/situation
  • Interactions related to external validity Does
    an independent variable have the same effect in a
    different situation or with different
    participants? (with the different situation
    represented by another factor).

Study 1
Study 2
RH
RH
Batter
Batter
LH
LH
Right-handed Pitcher
Left-handed Pitcher
16
Main Effects in American Idol
Yeah!! Go Corey!
Type of Song
Overall Avg.
Love Song
Rock Song
150
Main Effect of Sex F gt M
Male
Sex of Singer
Female
250
DV of votes (in thousands)
17
Graphing Results of Factorial Designs
For Main Effects Compute the averages for each
condition and plot as bar graphs Which is larger?
18
Graphing Results of Factorial Designs
For Interaction Effects Plot all of the data as
line graphs. Nonparallel lines indicate an
interaction.
Pitcher
19
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20
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21
Alcohol Study in Factorial Notation
Expectation
Alcohol
No Alcohol
Alcohol
4.3
Actually Get
4.2
No Alcohol
5.05
3.45
22
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23
Main Effects in Alcohol Study
24
Simple Main Effects
  • Simple main effects examine the effects of one
    factor at one level of another factor
  • E.g., do right-handed batters have higher batting
    averages than left-handed batters against
    left-handed pitchers?
  • Question is isolated to left-handed pitchers (one
    level of the pitcher handedness factor)

25
Simple Main Effects
Simple Main Effects of Batter Handedness at 2
levels of pitcher handedness
Pitcher Factor Level1
Pitcher Factor Level 2
RH
RH
Batter
Batter
LH
LH
Right-handed Pitcher
Left-handed Pitcher
26
Simple Main Effects in American Idol
Yeah!! Go Corey!
Type of Song
Overall Avg.
Love Song
Rock Song
150
Main Effect of Sex F gt M
Male
Sex of Singer
Female
250
DV of votes (in thousands)
27
Graphing Results of Factorial Designs
For Interaction Effects Plot all of the data as
line graphs. Nonparallel lines indicate an
interaction.
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