Q 703. Is using Control Charts necessary for every Lean Six Sigma project? Why / why not?

 

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Control charts are are charts which are shown with average, upper and lower control limits/lines to see whether process is stable or not.

Generally, the control charts are X-bar, R- bar used for continuous data such as measurements, weights and time. P - Chart and C- Chart used with discrete data such as Fail/Pass cases, number of customer complaints

Point-Using Control Chart is not mandatory for every Lean six sigma Gb or BB project in health insurance claim processing, but they highly beneficial and recommended.

 

Reason- Control Charts help in getting the process stability, data driven decision making, and recognize variations that required immediate corrective actions. But their need depends upon the specific goals and context of the project.

 

Example:

To reduce the time taken to process health insurance claim, Control charts can be a useful tool. It can easily check the average processing time and recognize the waiting time and variations in the process. If we get the output of control chart in acceptable limits then our process is stable. Or If the points are outside the control limits, then this is the special cause variations and that needs to be addressed. In contrast to this, If there is a small project which focuses in improving the interactions of customer service, then use of control charts might not be that critical. Moreover when the process is not involved in continuous monitoring.

 

In summary, Since control charts are a impactful tool in Lean Six Sigma, but their use should be checked based on the specific needs and context of the project .

Using Control Charts is not necessary for every Lean Six Sigma projects; however, Control Chart is a valuable tool in many scenarios:

1. Process Stability: Control Chart helps ensuring that a project is stable and predictable. It is very critical to sustain the improvements
2. Detecting the Special causes: It identify the unusual pattern or outliers. This indicates the potential issues we need to address
3. Quantifying the Variability: It helps team to reduce unnecessary variation by measuring process variability
4. Validating Improvements: Control charts help us to verify whether the implemented solutions have resulted into sustainable improvements or not
5. Visual Representation: Visual representations help in identifying process behavior over time

When should we use Control Chart:

• To optimize process with high variability we can use control chart
• To assess process stability, we can use control chart
• To monitor process performance over time we can use control chart

When not use control chart

• For a simple project where we have minimal historic data with less variation we can avoid using control charts                 
• If the resources are limited, we can prioritize other tools & techniques rather than control chart
• If the improvement is dealing with non-repetitive or one-time improvement, we can avoid using control charts
• Unavailability of proper measurable data do not qualify to use control charts

Although Control Charts are very powerful tool for Lean Six Sigma projects however the usage is highly dependent on project’s specific needs & goals. Control charts are highly appreciated when process stability, variability & sustainability are critical to the overall project success criteria.

A Control chart is a graphical tool that helps us study how a process is changing over time. Data are plotted in time order(i.e. X axis progressing in time), and consists of a central line representing the mean and the the upper/lower control limit(plotted along the Y axis). These lines, based on historical data, lets us compare current data to see if the process mean has shifted or not or the variation has increased/decreased.

It's a great visual representation of the process data over time and allows us to visually see how our processes are performing over time. It is one of the most commonly taught QC Tool (part of the 7 QC Tools) across industries segments. And a lot of LSS projects are focused on either :-
1. Shifting it's mean                    2. Reducing it's variation

Is it absolutely necessary to use Control Charts in LSS Projects?
Like most things in the real life scenarios, there are quite some nuances which has to be understood. Like,
 

1. What kind of project we are doing
Whether its' a DMADV or DMAIC project. Using Control charts makes more sense when there is historical data available. As it allows us to reliably calculate the process mean and control limits. In a DMADV project, we may refer control charts of older designs/processes for identifying opportunities for improvement, but cannot compare the newly designed processes with the old data as most DMADV projects target multiple improvements and focus on a lot more than a single process.
However, In case of DMADV, Control charts can be used during the Verify stage and during pilot runs of the new process which is addressed at following points

2. What sort of operation/process we are analyzing & Data Sources available
A lot of LSS Projects done by enabling functions such HR, Finance, Procurement etc., may have a lot of variables and non continuous data. In such projects we may be dealing with processes that aren’t continuous or where we don’t have sufficient data points to build a meaningful control chart. In these cases, simpler tools like Pareto charts, histograms, or fishbone diagrams may be more appropriate.
 

3. Timeline of the Project/Resources available
Many a times, we come across projects which have a short timeline with the focus to improve one metric or one process. In such projects, it makes more sense to drive the improvement check whether the process has improved and handover to the Process Owner. Though such projects can be labelled as strictly LEAN Projects, most of the time these projects are run under the larger Lean Six Sigma umbrella.
Also, it is common for the LSS professionals to be given ad-hoc projects to improve some particular operations or address some obvious special cause variations in a stable operation then the project can be resolved through proper Root Cause Analysis and a new Failure Mode Effect Analysis. In such cases also usage of Control charts is also an overkill which could divert resources.

These are just a few cases where the usage of Control charts may not be advisable.

So, in conclusion to answer this question, it is absolutely not necessary to use Control Charts during LSS projects, though they are one of the most common tools used in LSS projects.

Indrani has provided the best answer to this question by highlighting the areas where usage of control charts might not be advisable. Well done.

 

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