To understand variability and why it is a problem there is a simple tabletop game to play that is a great introduction to the variability within processes.

In Figure 1.1 two lines are drawn crossing at 90^o with a 2mm circle drawn around their intersection.  The game is to sit at a table and drop a pen into the two millimetre diameter circle from a height of around 300 mm (one foot).  Getting a hit within the circle is the outcome required from this ‘process’.  Repeat the targeting and drop process at least thirty times.   After each drop measure the position of the new mark to an accuracy of half a millimetre.  Record the horizontal distance from the vertical line (the ‘x’ distance) and the vertical distance from the horizontal line (the ‘y’ distance) in a table like that of Table 1.1.

Figure 1.1: The Crosshair Game

Observe the average and spread, of the ‘X’ and ‘Y’ results.   In Table 1.1 no hits are within the two millimetre circle; some are on or near the edge while most are well away.  Even though great effort was made to control the ‘process’, the results were across a wide band of outcomes.  This same problem occurs in all business and operations processes.  The outcomes of a process are spread across a range of results.   That is variability.  Variability becomes a problem for a business when the results from a process are not consistently within their required boundaries.

If the aim of the game is to have every pen-drop fall inside the 2mm circle, then we have a very poor process for achieving that outcome.  To get better results requires changing the process.  The game can be repeated using a different process.  The results in Table 1.2 were from a process where the pen was dropped after aiming it at the circle from above, much like dropping a bomb from an aeroplane using targeting sights.