Post on 17-Oct-2015
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Statistics One
2
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1:
2:
3:
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2~ 1
1:
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, 1 , ,
. , . Steven Pinker
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Polio Vaccine
In 1952, the first effective polio vaccin
developed by Dr. Jonas Salk How do we know that it was effective?
Experimental research! Randomized Controlled Experiments
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Polio Vaccine
Sample Initial
4,000 children from Virginia Final
1.8 million children from 44 states
Population All children in the USA
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Polio Vaccine
Independent variable Treatment
Vaccine Placebo
Dependent variable Polio diagnosis (measure of an individua Rate of polio (measure of a group of chil
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Polio Vaccine
Double-blind experiment Experimenter did not know if the treatm
vaccine or placebo
Child (and parents) did not know if thetreatment was vaccine or placebo
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Polio Vaccine
Results Rate (per 100,000)
Treatment: 28 Control: 71
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Polio Vaccine
By 1994 polio had been completelyeradicated from all the Americas
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Segment Summary
The major benefit of randomizedexperiments is they allow for strong c
about causalityWhy stuff happens!
Predict stuff Prevent bad stuff Promote good stuff
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Segment Summary
Strong causal claims require: True independent variables Random and representative samples
No confounds (impossible, but we try ou
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END SEGMENT
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Lecture 1 ~ Segment 2
Example 2: Memory Training
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Memory Training
Is it possible for adults to enhance thintelligence by training their working
memory? Promote good stuff!
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Memory Training
Sample College students
Population Healthy adults
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Memory Training
Independent variable Training
Memory training No training
Dependent variable Gain in score on an intelligence test
IQ gain
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Memory Training
Procedure Treatment group engaged in memory tra
for a half hour every day for weeks See next slide
IQ All subjects completed a test of intelligence
and after training
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Memory Training
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Memory Training
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Memory Training
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Memory Training
Does it really work? Potential confounds?
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Segment Summary
The major benefit of randomizedexperiments is they allow for strong c
about causalityWhy stuff happens! Predict stuff
Prevent bad stuff Promote good stuff
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Segment Summary
Strong causal claims require: True independent variables Random and representative samples No confounds (impossible, but we try ou
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END SEGMENT
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Lecture 1 ~ Segment 3
The concept of random
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Random
Experimental research requires: Random selection Random assignment
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Random
Random selection Individuals included in a sample should b
randomly selected from the population
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Illustration
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Random
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Not random
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Random
Random assignment Individuals are randomly assigned to con
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Random assignmentGroup 1 Group 2
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Segment Summary
Experimental research requires: Random selection Random assignment
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END SEGMENT
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END LECTURE 1