Cumulative Deviation

Maybe you have a day by hour chart, or sales plan vs. actual sales data and you want an easy way to decide when to take action - consider the simple Cumulative Deviation. First you need some data, two variables that you want to compare.  Here in this spreadsheet example we have Plan and Actual for eight time periods. Deviation is Plan - Actual.  In the first period we fell short of the Plan by 3 units.  I period 2 we did a little better and slightly exceed the plan (-1). Cumulative Deviation is adding the period deviation to the one preceding it. Here in period 2 we have (-1) + (3) = 2.  Drag the formula across all the columns and you now can more easily see that the deviations are growing. At some point, maybe we need to change the Plan, or do 5 Whys or Root Cause Analysis to better understand the cause and effect.