Flow Efficiency

In Kanban, Flow Efficiency (FE) helps you measure the actual work time against the Lead time. So, the efficiency can be measured by dividing Work Time by the combination of Work Time and Wait Time, and higher is the percentage, better and smoother is the process having less waste in the system and more agility to turn idea or request into a workable feature. 
In SwiftKanban, you can measure the percentage of time spent on the cards that are typically in the In-Progress column type against the total time those cards spend on the board. So, the formula for calculating Flow Efficiency percentage is:
Flow Efficiency in % = Work Time / ( Work Time + Wait Time)
Where,
Work Time = Time spent by a card in the ‘In-Progress’ Column types – The time the card was blocked in these columns
Wait Time = Blocked Time +Time spent by a card in the ‘Ready’, ‘Completed’ and ‘Done’ Column Type

Filtering the Data Set

  1. Navigate to Board > ESP Module, and then select the Lane and enter the start and end date for which you want to plot the chart.
  2. The chart is plotted based on the time cards spend on the board. 
  3. You can perform any of these activities to further refine your search and narrow down the scope of the chart:
  • Select any of these attributes: like Item Type, Priority, Size, or Class of Service to plot the chart. You can further refine your filter by selecting particular attribute values. For example, if you have selected ItemType as filtering attribute, then you can further select Change Request and Defect to narrow down the scope of the chart. 
  • You can also define the Start and End column to further filter your data on the chart.
As you apply any of these filters, the chart will be refreshed and rendered automatically.  

Reading the Diagram

  1. This is a feeder Flow Efficiency chart (image 1) where you can specify the date range by dragging the slider. 
  2. Based on the date range, as mentioned in step 1, the second last chart (image 2) places cards as dots on the Box-plot chart based on their flow efficiency percentage (Y-axes) ranging from 0 to 100% during the specified time range (X-axes).   
  3. The box-plot divides the cycle time range into quartile 1, Median and Quartile 3, and shows the cards (colored dots) that fall into or out of this range.
  4. Each dot represents a card and the color defines its card type, as defined in the board policy. Hovering over any dot will show the card id, flow efficiency percentage and the date.
  5. The span between the quartile 1 and 3 is called Interquartile Range or IQR. Generally, IQR is calculated as 1.35? where ? is the standard deviation.
  6. Any card that falls beyond 3×IQR or more above the third quartile or 3×IQR or more below the first quartile, is called Outlier. In the image 2, cards having 100% flow efficiency, are the outliers.
  7. The gauge or speedometer chart (image 3) points out how coefficient is the ratio between average flow efficiency and standard deviation for the selected date range (image 1). The coefficient is derived by dividing the Deviation by Average. Any coefficient rate which is 0.61 or below is acceptable on the board. Anything beyond 0.61 goes into Red and needs to introspection. 
  8. The Bar Chart ( image 4) plots the bar based on the ratio between the number of cards and flow efficiency percentage. For example, in image 4, 7 cards have achieved 100% flow efficiency, whereas another 7 cards have achieved efficiency in between 80%-90%. 

Interpreting the Diagram

Flow efficiency diagram the overall health of the flow efficiency of your Kanban cards. You can monitor whether most of the cards on your board do fall in between Quartiles and whether the variance is coefficient. Ideally, there should be fewer cards below Quartile 1 and more cards around or above Quartile 3 to provide that the project maintains a smooth execution of tasks with less waste.