Understanding Variation
"Systems constantly exhibit variation. We are forced to make decisions in our lives based
on our interpretation of this variation. Is my child's school improving? Does this month's
change in sales mean we are losing market share? Do the two medication errors this month
in our hospital indicate an undesirable trend? Was the improved performance this week the
result of the change we made or just luck? The ability to answer these questions and
others like them is inseparable from making improvements."
~ Langley, G., Nolan, K., Nolan, T., Norman C., Provost, L. 1996. The Improvement Guide:
Practical Approach to Enhancing Organizational Performance.
San Francisco: Jossey-Bass Publishers.
on our interpretation of this variation. Is my child's school improving? Does this month's
change in sales mean we are losing market share? Do the two medication errors this month
in our hospital indicate an undesirable trend? Was the improved performance this week the
result of the change we made or just luck? The ability to answer these questions and
others like them is inseparable from making improvements."
~ Langley, G., Nolan, K., Nolan, T., Norman C., Provost, L. 1996. The Improvement Guide:
Practical Approach to Enhancing Organizational Performance.
San Francisco: Jossey-Bass Publishers.
A control chart (above) is a statistical tool used to distinguish between variation
in a process due to common causes and variation due to special causes. It is
constructed by obtaining measurements of some characteristic of a process and
grouping the data by time period, location, or other process descriptive variables.
in a process due to common causes and variation due to special causes. It is
constructed by obtaining measurements of some characteristic of a process and
grouping the data by time period, location, or other process descriptive variables.