QUARTILES

Quartiles involve dividing a distribution of values into four equal parts. The top quartile is called the first quartile, and the bottom one is the fourth quartile.

Quartiling provides a convenient way to evaluate a distribution. It is also simple to apply.

for Dividing a Distribution into Quartiles

• Sort the distribution into either ascending or descending order.
  • Example (using sixteen observations):
    
    101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116
• Divide the total number of observations by four.
  
  16 / 4 = 4
• From the top (or left-hand side), count to the last observation in the top quartile, and draw a line.
  
  101, 102, 103, 104, | 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116
• From the value after the previous quartile, count the next 25 percent of the observations, and draw a line.
  
  101, 102, 103, 104, | 105, 106, 107, 108, | 109, 110, 111, 112, 113, 114, 115, 116
• Calculate the third quartile like the second quartile, and draw a line.
  
  101, 102, 103, 104, | 105, 106, 107, 108, | 109, 110, 111, 112, | 113, 114, 115, 116
  • Note: The remainder will be the fourth quartile.