What:
The PPM approach compares total defects to the total sample size and normalizes the data to a standard rate in order to evaluate a process = ( defective units / total sample size ) x 100
Where:
The overall sample size is equal to the sum of the defective and passed units.
A defective unit is one that doesn't match the requirements.
How:
Is a process being evaluated using ppm or %? What is superior?
Rule of thumb: Defect rate greater than 2% or 20,000ppm:
This gives all floor operators a better means of communication.
It is preferable to display flaws as a percentage in these cases since it is simpler to grasp. 30% Defective = 300,000ppm Defective.
Use a ppm to assess and explain the process when the fault rate is less than 3% or 30,000 ppm.
This offers a more effective instrument for progress.
Since this encourages improvement at lower quality levels, it is preferable to display flaws in these circumstances as a ppm.
