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Correlation

Correlation. Median HHI and Percent of Households Eligible for Food Stamps. Percent of Households Eligible for Food Stamps and Percent Unemployed. A few words about Scatterplots. A Scatterplot displays the direction and strength of the association between two sets of quantitative data

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Correlation

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  1. Correlation

  2. Median HHI and Percent of Households Eligible for Food Stamps

  3. Percent of Households Eligible for Food Stamps and Percent Unemployed

  4. A few words about Scatterplots • A Scatterplot displays the direction and strength of the association between two sets of quantitative data • The direction refers to whether there is a positive, negative, or no association between the data • The association is strong if the dots come close to being in a straight line • The association is weak if the dots don’t come close to being in a straight line

  5. A number called the correlation measures both the direction and strength of the linear relationship between two related sets of quantitative variables.

  6. Properties of Correlation • The correlation is written as r • Correlation requires that both variables be quantitative • A positive value for r means there is a positive relationship between the variables • A negative value for r means there is a negative relationship between the variables

  7. The value of the correlation is always between - 1 and + 1. • A strong relationship means the correlation is close to either - 1 or + 1 • There can be a strong positive relationship (r is close to 1), or a strong negative relationship (r is close to - 1) • A weak relationship means the correlation is closer to 0 than to either - 1 or + 1 • The value of r is affected by outliers

  8. Guess the Correlations:.67 .993 .003 -.975

  9. Excel Formula for Correlation: =CORREL(array1,array2) =CORREL(array1,array2) =CORREL(a1:a6,array2) =CORREL(a1:a6,b1:b6)

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