Quality Control: Run Chart vs Control Chart for PMP Exam

The PMBOK® Guide mentions the Seven Basic Tools of Quality for the Project Quality Management Area, these seven tools are:

• Cause-and-effect diagram (i.e. “fishbone” / Ishikawa diagram)
• Check sheet
• Control chart
• Histogram
• Pareto chart
• Scatter diagram
• Flowchart

Of these Seven Basic Tools of Quality, the Run Chart and the Control Chart are often confused by many Aspirants as these two look very alike. This post will answer the question: what are the similarities and differences between Run Chart and Control Chart. (Please note that this post is not a detailed discussion of run chart and control chart, it includes all that Aspirants need to know for theexam only.)

Run Chart vs Control Chart for PMP Exam

• Run Chart: A Run Chart simply plots the data of a variable over time.
  • Through analysis of a run chart, the following can be derived:
    • changes / trends of the process over time
    • any pattern / cycle of the process
  • Examples of a run chart:
    • progress of the project / processes / tasks (percentage completion over time)
    • expenditure of the project
  • Plus: A run chart is easy to draw and interpret. It is useful for analysis of simple processes.
  • Minus: Cannot show if the process is in control or stable. Not quite useful for quality control.
• Control Chart: A Control Chart also plots the data of a variable over time (same as the run chart), but also includes specification limits (Upper Specification Limit USL and Lower Specification Limit LSL) and control limits (Upper Control Limit UCL and Lower Control Limit LCL).
  • Specification Limits: provided in the project plan / contract as a project requirement of the process;
  • Control Limits: specified by the quality requirements of the process (e.g. 3-sigma); if a data go beyond the control limits or a pattern/trend has been formed, corrective actions must be taken to correction the deviation.
  • Tells whether the process is under control
    • Telltales of “Out of Control”:
      • Any data point outside the control limits
      • Rule of 7: 7 consecutive data points within the control limits but on either side of the mean
      • A trend has been formed (e.g. 6 consecutive points forming an increasing or decreasing trend)

To put it another way, a Control Chart is a Run Chart with 4 line indicating the limits added (upper/lower specification limits and upper/lower control limits) (plus optional a line indicating the mean of all data).

Run Chart vs Control Chart Illustrated

Below is a simple chart illustrating the difference and similarities between Run Chart and Control Chart:

Which one is run chart and which one is control chart?

Mock Exam Question

1. Paul, the project manager, is currently assessing the quality of a process of the deliverable. Which of the following charts/diagrams should he make use of when he wants to know whether the process is under control?
   1. Control Chart
   2. Ishikawa diagram
   3. Run Chart
   4. Pareto chart
   Solution: A
   The Control Chart is a run chart including the upper/lower specification limits and upper/lower control limits which are thresholds indicating whether the process is under control / meets the quality specified by the project.

   ---

Conclusion: Run Chart vs Control Chart

To put it simply:

• Run Chart: plotting the value of a variable over time to analyze the trend of a process
• Control Chart: basically a Run Chart by adding a mean, two specification limits (Upper Specification Limit USL and Lower Specification Limit LSL) and two control limits (Upper Control Limit UCL and Lower Control Limit LCL) to analyze whether the process is under control

Hope this article can illustrate the differences between Run Chart vs Control Chart well.

Additional FREE PMP resources: 47+ Commonly Confused Term Pairs with detailed explanations. If you found this article useful, you may wish to reference other Commonly Confused Term articles.