1.5 sigma shift (short term vs long term) suggests that if the process is left unchecked then certain level of inefficiencies will impact the overall performance of the process in long run... Is there a way of predicting how soon / late will that hap

1.5 sigma shift (short term vs long term) suggests that if the process is left unchecked then certain level of inefficiencies will impact the overall performance of the process in long run... Is there a way of predicting how soon / late will that happen in any manual process by using the current RTY and defect rate of that process.