Acceptable Quality Level, sometimes referred to as Acceptable Quality Limit, refers to the maximum number or percentage of defects allowed in a random product sampling.  The hypothesis of AQL only is validated if an acceptance sampling scheme has rules for changing between normal, tightened, and reduced inspections. These rules are intended to benefit suppliers to incorporate a process of averages which are consistently better than the AQL. If suppliers do not follow the rules, there is a chance of changing from a normal inspection to tightened inspection where lot acceptance becomes more difficult. If a tightened inspection occurs, it is very likely that the rule requiring discontinuance of sampling inspection will be invoked.