Senior managers at a client asked us to help them understand why the workload in
a particular team was increasing (at least that was their perception of what was
We were presented with nearly four years’ worth of data which managers would
typically present in a bar chart. What could you conclude from that? Probably not a lot.
If you want to understand any trends in “time series data”, you have to use line
graphs (“Run Charts” in SPC terminology). Better still; an SPC Control Chart will
highlight the real variation in the process.
We presented the data as a Control Chart (below).
This shows the process average during 2005-06 was 26 and from April 2006 onwards
was 38. Interestingly, there was almost twice as much variation in the process after
April 2006, as shown by the increased width of the Upper and Lower Control Limit
lines (UCL, LCL).
So, there is no evidence that the caseload is increasing, despite management’s
perceptions. There was a change at the beginning of 06-07 and it is known that
new legislation was implemented at that time and this caused the increase in
caseload, which has subsequently stabilised at a higher monthly level.
This is just one simple example where, if the right statistical tools are used,
management can gain much more insight into the performance of the organisation
and, potentially, avoid making the wrong decisions. In this case, there is no
justification for changing staffing levels to cope with the caseload.
Download the full article “Managing by Numbers: Statistical Thinking“.