a method of assessing performance at the end of a planning period
where performance does not meet expectations, corrective action should be taken, bringing performance back to the required level
as this is a more reactive approach,any adjustments will be delayed somewhat
avoids unnecessary delays in taking corrective action by taking action during the period rather than at the end of a period
whilst more difficult to implement, its advantage is that it allows for adjustments to be made as soon as deviations are noted
changes in production via control charts