W6_WAS_Fuel Consumption – SPC

Step 1- Problem or Opportunity Statement

Living in metropolitan city like Jakarta is a hard work, everyday is moving from one place to another place. That’s why we need an efficient fuel consumption vehicle.

I want to know if my vehicle’s fuel consumption is within control or not.


Step 2 – “FEASIBLE alternatives”

Herewith my fuel consumption data for 25 days, everyday from home to office. My journey is around 50 km in return.


Step 3- Develop the outcomes for each alternative (minimum 2)

From data above, we can transform daily fuel usage into line chart:


Then, I calculated Mean and Standard Deviation. The result are:

Mean : 9.64 km/lt

Std dev : 1.15 km/lt

Step 4- Selection of the acceptable criteria
From Mean and Std dev, Upper Control Limit (UCL) and Lower Control Limit (LCL) is calculated, and we get:


Step 5- Analysis/ Comparison of the Alternatives against the Criteria


The green line shows UCL, while red line shows LCL. My fuel consumption in 25 days are below UCL and above LCL.

Step 6- Selection of the Best/ Preferred Alternative Compared against the Criteria

The UCL, LCL only tells you that the readings you have got are in statistically under control or not.  So, from analysis, we knew that fuel consumption / gas mileage is statistically under control.

Step 7- Performance Monitoring and Post Evaluation of Result/ Follow up Assessment

Now that I already know my Control Limit, I can now analyze if my fuel consumption is not under control. Let’s say, if one day my gas mileage is 14 km/lt (above UCL), then I have to find out what is the cause. And I also have to maintain my car regularly.

These figure below, taken from http://www.doh.state.fl.us/hpi/pdf/Cause_and_EffectDiagram2.pdf, shows cause and effect diagram of Poor Gas Mileage:



Sullivan, William G., Wick, Elin M., Koelling, C. Patric. (2012), Engineering Economy. 15th ed., Pearson Higher Education, Inc.

Brassard, M and Ritter, D (2010), The Memory Jogger (2nd Edition), Canada, GOAL/QPC.

Giammalvo, PD. (2013). AACE Certification Preparation Course. Retrieved from http://www.build-project-management-competency.com/

Florida Health (). Basic Tools for Process Improvement; Module 5 ; Cause and Effect Diagram. [ONLINE] Available at: http://www.doh.state.fl.us/hpi/pdf/Cause_and_EffectDiagram2.pdf. [Last Accessed 28 September 2013].



by | October 1, 2013 · 22:51

3 responses to “W6_WAS_Fuel Consumption – SPC

  1. EXCELLENT case study and your calculations were done correctly, BUT…..

    Your analysis was only half done……. You did check to see if there were any EXTERNAL or “special causes”, which is good…… But what you missed totally was whether or not there are any INTERNAL or PROCESS problems….

    I will accept this posting provided for your W7 posting, you take the same case study (which was a very good one) and turn to pages 62 and 63 in your Memory Jogger 2. In your W7 posting, you need to do an analysis to determine if your fuel economy is out of control due to an INTERNAL problem-i.e your machine needs a tune-up or one of your fuel filters is clogged…..) Something that is happening to the process itself.

    This is the REAL value of using Statistical Process Control Charts, not just looking for outliers but in using it to monitor the “health” of the process itself.

    Suggest that BEFORE you write your W7 blog, you read Memory Jogger pages 530 – 70; oages 173 – 177 and pages 182-187. If you want to get 5 stars for your W7 report, make certain you cover all the key points contained in those additional readings. Show us you really understand how to use Control Charts. (And you have some really great data to use for other case studies on this topic from our Weekly Report as well)

    Dr. PDG

  2. Typo…… read pages 53-70; pages 173 – 177 and pages 182-187 in your Memory Jogger 2- THEN create your W7 posting…..

    BTW, you will THANK ME for making you do this as almost 100% certainty you will see a Statistical Process Control Chart problem on your AACE exams……

    Dr. PDG, Jakarta

  3. Dr. Paul.

    Sir Yes Sir! 😀
    Thank you for your input.


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