Lloyd S Nelson came up with 8 Nelson rules in the year 1984 addressing variability in a process or data beyond (+/- 3 points standard deviation from the process mean between the sub groups ). These are also called Special causes Variation or Non Random Variation. 8 Nelson rules helps in performing suitable control charts based on the relevant data type covering all the abnormalities in data to help work on assignable special causes & draw RCA & CAPA/Training. Special causes are generally due to sudden change in the process, machine, shifts, customer, Raw Material, Lot type etc. These kind of causes are normally associated to Manufacturing Industry due to unpredictability in nature.