The first is the weighted average of costs which assumes that all costs, regardless of whether they are accumulated in a previous period or in the current period, are grouped together and assigned to the units produced. The weighted average method is commonly used in cases where there is no standard costing system. The second is the FIFO method which means “first in first out”. FIFO costing is used when there are significant changes in product costs in each period. When this occurs, management must be aware of the new cost levels so they can reevaluate products appropriately, determine whether there are internal cost issues that require resolution, or whether changes need to be made based on manager performance