Step 7: Basic Process Capability

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Once you determine that a process has been stabilized, the data collected previously can be used again to determine process capability.

This time you plot the individual data points to produce a bar graph called a histogram. This histogram will be used to determine if the process is capable.

Once a histogram has been prepared simply superimpose the target value for the process on the bar graph.  

The target value and any specification limits are established in Step 1 of the quality improvement process.

HistogramHistogram With Specification Requirement

Once the data, the target value, and any specification limits (if applicable) are plotted, you're ready to determine whether the process is capable .

Use the following to guide your thinking:

  • Are there any unusual patterns in the plotted data?
  • Does the bar graph have multiple tall peaks and steep valleys? This may be an indication that other processes are influencing the process the team is investigating.
  • Do all of the data points fall inside the upper and lower specification limits (if applicable)? If not, the process is not capable. 
  • If all of the data points fall within the specification limits, are the data grouped closely enough to the target value? This is a judgment call. While the process is capable, you may not be satisfied with the results it produces. If that’s the case, you may elect to continue trying to improve the process by entering Step 8 of the quality improvement process.
  • If there are no specification limits for the process, does the shape of the histogram approximate a bell curve? After examining the shape created by plotting the data on the histogram, decide whether the shape is satisfactory and whether the data points are close enough to the target value. These are subjective decisions. If you're satisfied with both the shape and the clustering of data points, you can choose to standardize the simplified process or to continue through the remaining steps of the quality improvement process.

Quality Improvement Process - Basic Process Capability


From here to the end of the quality improvement process, you'll use another scientific methodology for conducting process improvement called the Plan-Do-Check-Act (PDCA) Cycle

You plan a change, try the change and collect some data, evaluate the data to find out whether the process improved, and decide whether to standardize or continue to improve the process. The PDCA Cycle is just that: a cycle. There are no limitations on how many times the team can attempt to improve the process incrementally.

Learn more about process capability here. See our

Quality Improvement Process


Step 1: Select the process to be improved and establish a well-defined process improvement objective. The objective can be established by the team or come from management.

Step 2: Organize a team to improve the process. This involves selecting the “right” people to serve on the team; identifying the resources available for the improvement effort, such as people, time, money, and materials; setting reporting requirements; and determining the team’s level of authority. These elements should be formalized in a written charter.

Step 3: Define the current process using a flow chart. This will generate a step-by-step map of the activities, actions, and decisions which occur between the starting and stopping points of the process.

Step 4: Simplify the process by removing redundant or unnecessary activities. It's likely that people may be seeing the process on paper in its entirety for the first time from Step 3. This can be a real "eye-opener" which will prepare them to take the first steps in improving the process.

Step 5: Develop a plan for collecting data and collect baseline data if it's not already being collected. This baseline data will be used as a "yardstick" later in the quality improvement process. This begins the
evaluation of the process against the process improvement objective established in Step 1. The flowchart in Step 3 is used to help determine who should collect data and where in the process data should be collected.

Step 6: Assess whether the process is stable. Create a control chart or run chart out of the data collected in Step 5 to gain a better understanding of what is happening in the process. Future actions of the team are dictated by whether special cause variation is found in the process.

Step 7: Assess whether the process is capable. Create a histogram to
compare the data collected in Step 5 against the process improvement objective established in Step 1. Usually the process simplification actions in Step 4 are not enough to make the process capable of meeting the objective and the team will have to continue on to Step 8 in search of root causes. Even if the data indicate that the process is meeting the objective, the team should consider whether it is feasible to improve the process further before going on to Step 14.

Step 8: Identify the root causes which prevent the process from meeting the objective. Use a cause-and-effect diagram or brainstorming to generate possible reasons why the process fails to meet the desired objective.

Step 9: Develop a plan for implementing a process change based on the possible reasons for the process’s inability to meet the objective set for it. These root causes were identified in Step 8. The planned quality improvement involves revising the steps in the simplified flowchart created after changes were made in Step 4.

Step 10: Modify the data collection plan developed in Step 5, if necessary.

Step 11: Test the changed process and collect data.

Step 12: Assess whether the changed process is stable . Same as Step 6, use a control chart or run chart to determine process stability. If the process is stable, the team can move on to Step 13; if not, you should return the process to its former state and plan another change.

Step 13: Assess whether the change improved the process. Using the data collected in Step 11 and a histogram, the team determines whether the process is closer to meeting the process improvement objective established in Step 1. If the objective is met, the team can progress to Step 14; if not, the team must decide whether to keep or discard the change.

Step 14: Determine whether additional process improvements are feasible. The team is faced with this decision following process simplification in Step 7 and again after initiating an improvement in Steps 8 through 13. In Step 14, the team has the choice of embarking on continuous process improvement by reentering the model at Step 9, or simply monitoring the performance of the process until
further improvement is feasible.


14 Step Quality Improvement Roadmap

Quality Improvement Process Roadmap

From Basic Process Capability to Quality Improvement Process

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