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Lecture
Experimental Design
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Correlational designs examine the relationship between two variables

Just because there's a correlation, that doesn't mean it's causal

The more time spent on reading, the higher reading achievement scores
Positive correlation:
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Don't know which one is causing which
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Directionofcausation problem
Both things could be caused by a common third variable
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Thirdvariable problem
Correlation does not equal causation
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The relationship between two variables is known as their correlation

Correlation
Index of strength and direction of relation
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Varies from 1.00 to +1.00
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+.70 and .70 are equally strong and both are stronger than +.35 and .35
Strength indicated by absolute value
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0 = no correlation
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What is r?

Direction indicated by sign
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+ means that one increases, the other also increases
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 means that as one increases, the other decreases (an inverse relationship)
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More about r

Need to know what it is, and how to interpret it

General Research Designs
Greater time spent reading might mean higher reading score, BUT greater reading skill can
also motivate the child and lead to more time spent reading.
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Correlation does not tell you directionality:

There may be a third variable

Correlation does not equal Correlation
Correlations + Experimental Design
January1413
12:02 PM
Intro to Child Development Page 1
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