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Chapter 15: Correlation - Coggle Diagram

- - - - used when a researcher wants to measure the consistency of a relationship between X and Y, independent of the specific form of the relationship
      - used when the original data are ordinal
      - Ranking tied scores:
        
        List the scores in order from smallest to largest. Include tied values in the list
        
        Assign a rank (first, second, etc.) to each position in the ordered list
        
        When two (or more) scores are tied, compute the mean of their ranked positions, and assign this mean value as the final rank for each score
  - - - Steps:
        
        Find the X deviation and the Y deviation for each individual
        
        Find the product of the deviations for each individual
        
        Add the products
- - - - Perfect correlation- always identified by a correlation of 1.00 and indicates a perfectly consistent relationship
      - Correlation of 0= data points scattered randomly; no trend
      - Intermediate values- between 0-1 indicate the degree of consistency
    - - Negative correlation- the two variables tend to change in the opposite direction
      - Positive correlation- the two variables tend to change in the same direction
    - - Linear- points on scatter plot tend to cluster around a straight line; most common
  - - - Coefficient of determination (r^2)- measures the proportion of variability in one variable that can be determined from the relationship with the other variable
      - Partial correlation- measures the linear relationship between two variables by eliminating the influence of a third variable by holding it constant