Homework 6: Correlation and Regression

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Homework 6 Correlation and Regression

• What is the strength of the relationship between
  two variables?

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What statistical test to use?See pg 25 of
lab manual
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Correlation

• No cause-and-effect
• No independent and dependent variables
• Variable axes are interchangable
• Statistic r
• ranges from -1 to 1
• 0 no relationship
• -1 or 1 perfect relationship

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Homework 6 Correlation and Regression

• What is the strength of the relationship between
  two variables?

r 0
r 1.0
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What is the strength of the relationship between
two variables?
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Regression 1

• Cause-and-effect
• Independent (x-axis) and dependent
• (y-axis)
• Statistic R2
• Ranges from 0 - 1
• 0 no cause-and-effect
• 1 perfect cause-and-effect

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What is the strength of the relationship between
two variables?
R2 0.99 r2
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Regression 2

• Generates a line to best represent points
• Can use linear equation to predict
• y from x
• y a bx a y-intercept b slope

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An example
Background Winters have been getting
warmer. Warmer air holds more moisture -- gt
snow. Does amount of snow predict robin arrival?
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If robins cue their upward migration on warm
temperatures,then robins will arrive earlier in
years with greater snowfall.Assumption
Warmer winters have greater snowfall.Go
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