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Lecture

Experimental Design

by

Department
Psychology
Course Code
Psychology 2110
Professor
Fangfang Li

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Correlational designs examine the relationship between two variables
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Just because there's a correlation, that doesn't mean it's causal
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Positive correlation:
Don't know which one is causing which
Both things could be caused by a common third variable
Third-variable problem
Correlation does not equal causation
The relationship between two variables is known as their correlation
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Correlation
Index of strength and direction of relation
Varies from -1.00 to +1.00
+.70 and -.70 are equally strong and both are stronger than +.35 and -.35
Strength indicated by absolute value
0 = no correlation
What is r?
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Direction indicated by sign
+ means that one increases, the other also increases
- means that as one increases, the other decreases (an inverse relationship)
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Need to know what it is, and how to interpret it
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General Research Designs
Correlation does not tell you directionality:
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There may be a third variable
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Correlation does not equal Correlation
Correlations + Experimental Design
January-14-13
12:02 PM
Intro to Child Development Page 1