Correlation
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Correlation. Topics. Measure of Relationship Strength Direction Scatterplot Conceptual Formula Computational Formula Assumptions Problems Effecting the Interpretation of the Correlation Coefficient. Measure of Relationship.

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Correlation

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Correlation

Correlation


Topics

Topics

  • Measure of Relationship

    • Strength

    • Direction

  • Scatterplot

  • Conceptual Formula

  • Computational Formula

  • Assumptions

  • Problems Effecting the Interpretation of the Correlation Coefficient


Measure of relationship

Measure of Relationship

  • In a correlational study, two measures -- representing the variables of interest -- are given to onegroup of subjects.

  • The subject’s scores on both measures are summarized, and the relationship between the scores on the two measures is examined.


Measure of relationship1

Measure of Relationship

  • When the correlation coefficient is used to describe a linear relationship, the coefficient can take on values from -1.00 to +1.00.

    • The sign of the correlation indicates the direction of the relationship between two variables.


Measure of relationship2

Measure of Relationship

  • A positive relationship means that low scores on X go with low scores on Y whereas high scores on X go with high scores on Y.

  • A negative relationship means that as scores on X increase, scores on Y decrease.

  • The absolute magnitude or size of the correlation coefficient -- that is, ignoring the plus or minus sign -- indicates the strength of the relationship between X and Y.


  • Measure of relationship3

    Measure of Relationship

    • A correlation of +.95 or of -.95 indicates a very strong relationship between the two variables.

    • A correlation of 0 indicates that there is no linear relationship between the variables.

  • Guilford's suggested interpretations for values of r.


  • Computation

    Computation


    Conceptual computational formulas

    Conceptual / Computational Formulas


    Computation conceptual formula

    Computation / Conceptual Formula


    Conceptual formula

    Conceptual Formula


    Computation computational formula

    Computation / Computational Formula


    Computational formula

    Computational Formula


    Problems effecting the interpretation

    Problems Effecting the Interpretation

    • Non Linear Relationship


    Problems effecting the interpretation1

    Problems Effecting the Interpretation

    • Outliers


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