Correlation Analysis

• Correlation - refers to a mutual relationship or association between quantities.
• Correlation Analysis - specifically used to measure the degree of linear relationship and association between two variables
• Positive Correlation - if an increase in the values of one variable results , on average, in a corresponding increase in the values of the other variable.
• Negative Correlation - if the variables derivate in opposie direction
• No Correlation - when there is no linear dependence or no relation between two variable
• Correlation Coefficient (r) - a summary measure that describes the extent of the statistical relationship between two interval or ratio level variables

  • is scaled so that it is always between -1 and +1
  • when r is close to 0 means that there is a little relationship between the variables and the farther away from 0 r is , in either the + or - direction, the greater the relationship between the two variables
• Scattergram - a graphical display that shows the relationship between two numerical variables which are presented by points or dots for each pair of score
• Scatter graph - indicates the strength and direction of the correlation between the co-variables