Transcript Types of Inferential Statistics

Research Design & Analysis 1
Class 16
Announcements
– Honours meeting
Dr. Sonya Symons
Today4:30-5:30 Horton -- Room 215
– Tutors
– Schedule changes
Correlation - print-outs & simulations
Introduction to experimental designs
– examples from memory research
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
1
Reading your SPSS printout
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7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
2
Venn Diagrams
Total variance in X(=1)
Total variance in Y(=1)
r2xy =0
Can indicate co-variation between variables
by the degree of overlap
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
3
Venn Diagrams
r2xy =.45
Total variance in Y(=1)
Total variance in X(=1)
Indicate co-variation between variables by degree of overlap
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
4
Venn Diagrams
r2xy =1.0
Total variance in Y(=1)
Total variance in X(=1)
Indicate co-variation between variables by degree of overlap
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
5
Drawing Conclusions From Correlational
Designs
All the same concerns as with experiments
(valid, reliable measures, etc.)
Additionally, have concerns with directionality,
and there are usually many potential
confounds (uncontrolled extraneous
variables - the 3rd variable problem)
Causality can not be inferred
Correlational designs can be used to:
– discover relations
– to solve ethical and practical problems
– to provide greater external/ecological validity
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
6
Characteristics of a scientific
experiment
• Manipulation (of the IV)
• Control (of extraneous variables,
potential confounds)
• Measurement [of the DV(s)]
• Comparison (of the measurements
with the appropriate statistics)
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
7
Experimental Designs
Types
• Between-subjects
• Within-subjects
• Single-subject
Issues: Error variance
Single-factor randomized groups
design
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
8
Anatomy of an Experiment
Possible Subjects
Random Assignment
(controls for subject differences)
Experimental Group
Control Group
Study and testing conditions
Study and testing conditions
Music
Behaviour
7/21/2015
Independent
variable
No Music
Test scores
(DV)
Behaviour
Psyc2013 Class #16 (c) Peter
McLeod
• Identical,
controls for
extraneous
variables
9
Model of Human Memory
Sensory Memory
Unattended
information
Attention
Working memory
Forgetting
Incoming
information
Retrieval
Rehearsal
Encoding
Long term memory
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
10
Hypothesis Generation
• Interested in amnesia (e.g., read about
“lost Mariner - Oliver Sacks)
• Effects of “shock” on memory
(electro-convulsive therapy - ECT)
• Wonder if an emotional shock will cause
retrograde amnesia?
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
11
Converting Question to an Analytical
Experiment
• operational definitions
• subject selection
• subject assignment
– within
– between
– matched
• variety of “mechanical details”
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
12
Experimental Hypothesis
• An emotional shock will disrupt memory for
events that occur immediately prior to
occurrence.
• Which words require operational definitions?
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
13
Experimental Hypothesis
• An emotional shock will disrupt memory
for events that occur immediately prior to
occurrence.
• Final, operationally valid version:
An unexpected 15-second scene that portrays
a mutilated body at the end of a 10 minute
travel film will disrupt a person's memory of
the price of 10 items listed in the film during
the one-minute period immediately
preceding the final scene.
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
14
Why Operational Definitions?
• avoid confusion
• makes study reproducible
• makes measurements reliable
But
trade off between precision of an
operational definition and it’s
construct validity
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
15
Converting Question to an Analytical
Experiment
• operational definitions
• subject selection
• subject assignment
• variety of “mechanical details”
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
16
Final Experiment
20 intro psychology subjects, 10 randomly
assigned to each group
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Experimental group
Control group
Male experimenter
• Male experimenter
written instructions
• written instructions
10 min travel film
• 10 min travel film
1 o’clock testing
• 1 o’clock testing
group testing
• group testing
15 s final scene version ‘a’ • 15 s final scene version
- mutilated body seated in
‘b’ - craftsperson
chair (operational defn’ of
weaving a basket - I.V.
emotional shock) - I.V.
• Measure memory Measure memory - D.V.
D.V.
Statistically Compare differences in measured memory
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
17
Loftus and Burns 1982
Loftus, E., & Burns, T. Mental shock can
produce retrograde amnesia. Memory and
Cognition, 10, 318-323.
Model of human memory
Sensory Memory
Unattended
information
Attention
Working memory
Forgetting
Incoming
information
Retrieval
Rehearsal
Encoding
Long term memory
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
19
Free recall memory task
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
20
Word Memory Stimuli
COMFORT
SLUMBER
AWAKE
DREAM
SOUND
SNORE
NIGHT
TIRED
WAKE
EAT
BED
REST
7/21/2015
Psyc2013 Class #16 (c) Peter
McLeod
21
Test stimuli
AARDVARK
SOUND
SNORE
SLEEP
7/21/2015
REST
TIRED
AWAKE
DREAM
SNORE
BED
EAT
SLUMBER
SOUND
COMFORT
WAKE
NIGHT
Psyc2013 Class #16 (c) Peter
McLeod
22
Model of human memory
Sensory Memory
Unattended
information
Attention
Working memory
Forgetting
Retrieval
Rehearsal
Encoding
Long term memory
7/21/2015
Incoming
information
Psyc2013 Class #16 (c) Peter
McLeod
False
Memories?
23