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Correlation

Correlation. AP Statistics Ch . 7 Day 2 EQ: What is the correlation coefficient and how do we find it?. Learning Target. How do we find the correlation coefficient and interpret it?. Warm Up. Book P. 165 # 12. Correlation.

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Correlation

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  1. Correlation AP Statistics Ch. 7 Day 2 EQ: What is the correlation coefficient and how do we find it?

  2. Learning Target How do we find the correlation coefficient and interpret it?

  3. Warm Up Book P. 165 # 12

  4. Correlation • Measures the strength and direction of the linear relationship between two quantitative variables. • We use the variable r to talk about correlation.

  5. When computing correlation, we have to standardize both the x values and y values first, which makes the scales on the axes standard deviation units.

  6. Compareand Contrast the Formulas

  7. Properties • Correlation is between -1 and 1. • Correlation has no unit of measure • Correlation is strongly affected by outliers • Association: Weak, Moderate, Strong

  8. Indicate whether you would expect a positive, negative, or no correlation. Explain. • Interest rate and number of loan applications • Height and shoe size • Score on a math section of the SAT and score on the verbal section of the same test. • Maximum daily temperatures and cooling costs

  9. Conditions for Correlation • Quantitative variables • Straight enough-must be linear • Outliers-report correlation with and without these values

  10. Steps for each correlation problem • State what you are investigating • Identify the variables • Make a scatterplot • Show work • Conclusion-Describe direction, form, strength, unusual features, state in context

  11. L1 = x L2 = y L3 = standardized x values L4 = standardized y values L5 = L3 * L4 Find the correlation.

  12. The following data on sale price(in milions of dollars), size(in thousands of square feet), and land-to-building ratio for 10 large industrial properties that appeared in a paper. • Make a scatterplot of the data and describe it. • Calculate the correlation between sale price and size. • Calculate the correlation between sale price and land-to-building ratio.

  13. D. If you wanted to predict sale price and you could use either size or land-to-building ratio as the basis for making predictions, which would you use? Explain.

  14. What is one thing you knew before today? What is one thing you learned today?

  15. HW Assignment p.166 # 16, 40

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