Variation due to assignable cause in product occurs due to difference in Total quality management policies of a firm. Variation in strict maintainence and implementation of quality ensuring techniques like quality check, quality circles, kiazen etc leads to variation in assignable cause in a product. Since the assignable cause refers to a detectable error at the firms level, and this occurs due to non complaince of check at the very first level of oocurence rather than identifying when the product is made. Hence the variation in assignable cause is due to variation or lack in quality checks