The most accurate and time-consuming estimating method: involves sealing estimates which are based on other project estimates upward or downward involves sorting detailed cost estimates by activity and then subtotaling activities to determine the cost for each activity uses the statistieal relationship that exists between historieal data and a particular delineated lint of other variables is to identify the cost of each item in each activity of the schedule, inchuding labor and materials the actual costs from previous projects as a basis for cstimating the costs for the current project