why is the high low method considered unreliable 
because it only considers two extreme activity levels the high or low points used for the calculation may not represent the costs normally incurred at those volume levels due to outlier costs that are higher or lower than would normally be incurred the high low method will then produce inaccurate results the bottom linethe high low method is a simple way in cost accounting to segregate costs with minimal information the high low method involves comparing total costs at the highest level of activity and the lowest level of activity after each level is determined 