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Correlation
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Correlation

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  1. Correlation

  2. Correlation Coefficient (r) Quantitative assessment of the strength of the relationship between x & y. It is the measure of the extent to which x & y are linearly related. *It is strong if the points lie close to a straight lint and is weak if they are widely scattered about a line.

  3. Correlation (r) • It’s a number between -1 and 1. • The closer it is to the ends, the stronger the positive or negative relationship. • It gives the strength and direction. Strong Negative No Correlation Strong Positive -1 1 0

  4. Let’s explore…. • www.whfreeman.com/tps4e

  5. Pearson’s Correlation Coefficient Think about z-scores of the x & y

  6. Pearson’s Correlation Coefficient Think about z-scores of the x & y

  7. Pearson’s Correlation Coefficient Think about z-scores of the x & y

  8. Correlation Coefficient r

  9. Find the correlation coefficient.

  10. Find correlation coefficient.

  11. AP Exam Tip If you are asked to interpret a correlation start by looking at a scatterplot of the data. Then be sure to address direction, form, strength, and outliers and put your answer in context.

  12. Properties of “r” • It does not depend on the unit of measurement. • It doesn’t depend upon which of the 2 variables is “x” • It’s between -1 and 1 • It equals -1 or 1 if all points lie on a straight line • It is strongly affected by a few outliers

  13. Scatterplots show relationships – not cause and effect.

  14. Try One! • Create scatterplot • Find the correlation • Describe the association

  15. Homework • Page 160 (14-18, 21, 26)