CORRELATION AND REGRESSION ANALYSIS

• Univariate Data - data involve a single variable.
• Bivariate Data - data that involve two variable.
• Correlation Analysis - is a procedure or process of describing the relationship between two variables.
• Scatter Plot - is a graphical representation of the relationships between two variables.
• The relationship between two variables is described in

  terms of strength and direction.
• Positive Correlation

  A positive correlation exists if high

  values in one variable are associated

  with high values in another variable.

  Similarly, low values in one variable are

  associated with low values in one

  variable.

  If a positive correlation exists, then the

  points on the scatter plot closely follow a

  straight line slanting up to the right.
• Positive Correlation

  
• Negative Correlation

  A negative correlation exists if high

  values in one variable are associated

  with low values in another variable.

  Similarly, low values in one variable

  are associated with high values in

  one variable.

  If a negative correlation exists, then

  the points on the scatter plot closely

  follow a straight line slanting down

  to the right.
• Negative Correlation

  
• Zero Correlation

  A zero correlation exists when

  high values in one variable are

  associated to high or low values

  in the other variable.

  If a zero correlation exists, then

  the points on the scatter are

  randomly scattered. The points do

  not follow closely a straight line.
• Zero Correlation

  
• Types of Correlation According to Strength

  • Perfect Positive Correlation
  • High Positive Correlation
  • Low Positive Correlation
  • Perfect Negative Correlation
  • High Negative Correlation
  • Low Negative Correlation
• Positive Correlation exists between two variables when the points on the scatter plot follow straight line slanting up to the right.
• Negative Correlation exists between two variables when the two pints on the scatter plot follow straight line slanting down to the right.
• Perfect Correlation exists between two variables when the two points on the scatter plot lie on a straight line.