Suresh Jayaram

Let me briefly talk about one of the tools (MGPP). MGPP stands for Multi-Generational Project Plan. If you think of the NASA space program of landing a man on the moon, it was not achieved in one step or generation. There were several generations - the first generation (Mercury program) tested the capability of putting a life in sub-orbit and safely bringing it back to earth. The second generation consisted of testing spacecraft for extended periods of time in space with docking etc (Gemini program) and the third generation was used to land a man on the moon (Apollo program). (Ref: http://www.apollo-society.org/shootmoon.html ) Similarly, on Six Sigma projects that have significant scope, it is a good idea to break up the scope into multiple generations. An MGPP helps a team focus on the current generation and also plan for what is to come in the future generations. For more details, you may want to refer to a good book on DFSS. Best Regards, SJ

Dear Saunak, Are you asking how to calculate the P values for Chi-Square test? SJ.

Dear Yoganandan, SIPOC is a high level process map that helps in identifying the key steps in the process along with the key stakeholders. A VSM is a lot more detailed map that can help with identification of problem areas. SJ.

Dear Ari/Ramabadran, You have rightly pointed out the Cpk cannot be translated directly into Sigma levels. Here are some additional points regarding that topic. Cpk (unlike Cp) includes both variation and shift to calculate the process capability. The traditional formula for Cpk (for a normally distributed process data) is given by: Cpk = min [ (USL - Xbar)/(3*S), (Xbar - LSL)/(3*S)] Where, LSL and USL are the Lower and Upper Specification Limits (as determined from the customer), Xbar is the average of the process data, and S is the sample standard deviation. When, we look at the formula, we see that we compute the minimum. Which means, we are looking at the defects that are greater than USL on one side and the defects that are less than the LSL on the other side and only picking the worst case (A smaller process capability number relates to larger number of defects). So, if a process had 10,000 PPM defects to the left of LSL and 20,000 PPM defects to the right of USL, then Cpk will look at both of them and then compute the process capability number related to 20,000. As pointed out earlier, Sigma Level (Bench) looks at defects on both sides and adds them up. So, it would not be directly possible to translate Cpk numbers to Sigma Levels. However, assuming the worst case defects occurs on both sides, it would be possible to estimate a conservative estimate of Sigma level if we so desire. Example: Let's say LSL = 11.5, USL = 18, Xbar = 15, S = 1. Cpk = min[(18-15)/(3*1), (15-11.5)/(3*1)] = min[1, 1.167] = 1.0 CpU (only looking at USL) = 1.0 CpL (only looking at LSL) = 1.167 PPM_U (only looking at USL) = 1350 PPM_L (only looking at LSL) = 232 PPM_Total (both sides) = 1582 Sigma_U = 3.0 Sigma_L = 3.5 Sigma_Bench = 2.95 Conservative estimate for Sigma_Bench based on Cpk = 1.0 (assume both sides have PPM = 1350 - centered process!). Hence, Total PPM = 2700 => Sigma_Bench = 2.78. CONCLUSION: Cp * 3 gives you sigma level on one side (Z_LSL and Z_USL). Cpk cannot be directly translated into sigma level for bilateral tolerances as it only looks at the worst side. Of course, if it is a unilateral tolerance, then we can predict Sigma levels from Cpk numbers.

Dear Sripathy, I agree - instead of thinking about them as suppliers, maybe we should consider them as process partners. We need to limit the number of partners we work with and jointly work with them to improve their (and our) performance. SJ

Dear Fazal, Individual project based assistance is only provided to past participants of Benchmark Six Sigma. If you are a past participant (been through Benchmark Six Sigma training), then please post your request on the forum for past participants and I would be glad to help. Best Regards, SJ>

When people talk about Sigma levels, they usually refer to Z (Bench) where defects on both sides (greater than USL, and less than LSL) are included. In the above formulation, we are only talking about Sigma level on one side. So, for a Cp = 1.0, the Sigma level for defects greater than USL is 3.0 and Sigma level for defects less than LSL is 3.0. The total Sigma level (bench) is 2.78. SJ

Dear Sandeep, There is a more complex formula and explanation that goes with your first question, but let me just say that as a rough guideline 3 * Process Capability = Sigma Level. So, if Process Capability = 2, then Sigma Level = 6 etc. Cpk stands for short term (within) process capability and Ppk stands for long term (overall) process capability. SJ

Dear Amit, There are lots of tools in Six Sigma (> 50) and it would be a really long post to explain these tools. I would recommend that you get a introductory book on Six Sigma and read through that book for understanding the basic concepts. Or, you could also sign up for a GB training session to learn the finer points of these tools. SJ

I recently saw a question on the open forum that asked about process capability numbers (Cp/Cpk) and Sigma Levels. I thought it was a good topic for us to discuss here. Are they related and if so, how do we translate from one to the other?

Dear Brijesh, Value Stream Mapping (VSM) is one of the advanced tools within Lean that can be used to make breakthrough transformation from the current state to a future state. It builds on the process map taught in Six Sigma courses and adds a lot more information to it. It includes both product flow and information flow in the same map. Certain metrics like Cycle Time (CT), Lead Time (LT), number of people working, quality issues, efficiency, etc. are highlighted on the map so that the viewer can quickly focus on the pain areas. At the bottom of the map is a Lead Time / Cycle Time chart which highlights bottleneck processes and the overall process cycle efficiency. An excellent book (though manufacturing focussed) is Learning to See by Mike Rother and John Shook. If you are interested in learning and applying VSM, it is a tool that is taught in our 2-Day Lean training course. Best Regards, SJ

Dear Kapil, If you go through a Black Belt program that is 10 days long, then you could do the Black Belt without doing the Green Belt. In these courses, the entire material that includes Green Belt and Black Belt is covered. At Benchmark Six Sigma, you can enroll for 10 days Black Belt directly at a special fee. In such a case you shall be learning with a 4 day Green Belt batch initially and continuing later with a 6 day Black Belt upgrade (exclusively for Green Belts) batch. Hope this helps answer your question. Best Regards, SJ

Dear Ari, I have seen water bottles that have an inner seal that has to be torn open after you open the cap and bottles that have a pull type cap (rather than turn open) which you can suck from. SJ.

Dear Sandeep, A 3.4 long-term DPMO corresponds to 4.5 Sigma level in the long term and 6 Sigma level in the short term. A 1350 long-term DPMO corresponds to 3.0 Sigma level in the long term and 4.5 Sigma level in the short term. There is no specific timeframe to indicate what is short term and what is long term. It varies from process to process. If a process has only common cause variation for one month but special causes can impact this process month over month then one month could be considered short term. If another process has common cause variation for 1 week but special causes impact it week after week, then one week could be considered short term data. So, you will have to look at your process to determine what is short term and long-term. Ideally, all trends, seasonality, and all types of special causes should be accounted for in the long-term so that long-term DPMO numbers are accurate. Generally, 6 months to 1 year can be considered long term. SJ.

Dear Sandeep, The 1.5 Sigma shift has been introduced to explain the difference between short term and long term performance. It is hypothesized that over a long period of time things could deteriorate due to poor process control or due to special causes that affects process performance. Hence, a process that is operating at 6 Sigma in the short term will only operate at 4.5 Sigma in the long-term. Thus, a process that is operating at 6 Sigma (in the short term) corresponds to 3.4 DPMO in the long term! When, people report Sigma levels, more often than not, they report the short term sigma levels (everyone wants to look good!). Practically, all companies use the 1.5 Sigma shift in their reporting and just to be consistent with the rest of the industry, it is recommended that you also use the 1.5 Sigma shift in your calculations. In conclusion, when you have the long-term data and you compute DPMO numbers and Sigma levels, you get the long-term numbers. Add 1.5 to this number and then report your Sigma level for your process to the rest of the world. SJ>

Dear Brijesh, You may want to create a Value Stream Map (VSM) of your entire process from your supplier to your delivery of diamond blades to your customers. This will enable you to identify bottlneck processes / areas to work on. SJ.

Dear Rishab, One of the most important CSF is top management commitment and support. One way to check is to walk on the shop floor or workplace and ask how many times do they see senior management walk up to them and ask how things were going? Do they participate in periodic reviews of Lean progress? Do they give any importance and resolve issues brought to their notice? Have they appointed Lean coordinators to help with Lean deployment? Are there rewards and recognition for Lean accomplishments etc. SJ.

Just to bring about a discussion, I would opine that inspection is not all bad. In the Lean philosophy, we rely on inspection to ensure that only good quality product is passed on to the next step in the process. If there are two steps in the process A followed by B. Then A inspects incoming material, does his work, inspects it to make sure everything is okay and then sends it to B. B follows the same process of inspecting the part that he/she has received, does work, and then inspects again before sending it out of his/her area. Quality at the source is very important and even if we have perfect processes, Poka-Yoke etc, we still need to spend maybe a few seconds at least to inspect incoming and outgoing work. Your thoughts on the above?

Design for Six Sigma (DFSS) is a Six Sigma methodology that is used to launch new products & services on time, on budget, and on target gaining incremental revenues sooner, achieving greater market share, and ensuring that the company generates differentiated products & services that target customer & stakeholder needs. DFSS methodology is most commonly used in New Product Development organizations. There are several approaches to DFSS, but the most popular methodology is called DMADV. DMADV stands for "Define - Measure - Analyze - Design - Validate". The Define phase consists of defining the project charter which includes the business case and the opportunity for the new product or service. In the Measure phase, the needs of the key stakeholders are identified and measurable CTQs are developed. The Analyze phase consists of subsystem design and generating and selecting the best possible concepts. In the Design phase, a detailed design for the product or service is developed and optimized. The robustness of the design is ensured to minimize the impact of variation on performance of the product or service. Finally, in the Validate phase, the generated designs are verified and validated using simulation and other approaches. Some of the tools covered in DMADV training are: Multi-Generational Project Plans (MGPP), Analytical Hierarchy Process (AHP), Kano Analysis, Kansei Engineering, Theory of Inventive Problem Solving (TRIZ), Quality Function Deployment (QFD), Pugh Analysis, Multiple Regression Analysis, Fractional Design of Experiments, Taguchi Optimization, and Discrete Event Simulation methods. DFSS is a powerful set of tools and techniques that can help you develop products and services that truly satisfy your key stakeholder needs. By adding this toolkit to your repertoire, you can demonstrate to your current or future employer that you understand how to not only reduce the bottom line costs using DMAIC but also develop robust products and services to increase top line growth using DFSS.

The LSL and USL are based on individual values and not on averages. Hence, when we set targets for our projects we should not be looking at averages but both the average and the standard deviations. For example, if the USL = 10, then any measurement that falls greater than 10 is a defect. If we have 4 series of measurements 8, 11, 8.5, 11.5, the average would be 9.75 (less than USL) but we have two out of the four measurements that are out of spec (50% defective). When setting up a target, we need to set the mean such that individual values don't cause too many defectives. For our example, where xbar = 5, s = 2, USL = 4 If we desire a performance with Cpk = 1.33 (Sigma Level = 4), then just by reducing the average alone we will not be able to achieve our goal (as mentioned by a few members). We would have to reduce both the mean and standard deviation in this problem. For example, if we are able to reduce the standard deviation to 0.5 and adjust the mean to 2 minutes, we would achieve our objectives (assuming normal data). Hence, one solution to this problem is reduce the mean to 2.0 and standard deviation to 0.5. Of course, we can have several combinations of the above to meet our requirements. Any other thoughts on this problem?

Dear Gaurav, There are several points to consider in order to develop and analyze surveys. I would recommend you to look up some good books on survey design and analysis. Here are some points to consider: a) What type of data do you need from your customer/organization? What is the best method to get it (focus groups, telephone survey, internet survey, face to face discussions, observations etc) c) Should you use open ended or closed ended questions d) What is the minimum number of samples required for appropriate analysis e) How to avoid bias in surveys f) How to analyze survey results (graphically, analytical tools such as Chi-Square etc) This topic is more appropriate for participants who have been through Green Belt or Black Belt training. Please post on Benchmark private group any further discussions on this topic. Best Regards, SJ.

Dear Namrata, Would your organization let you work on a project and implement its findings? As you indicate there are a lot of problem areas - so if you pick a project that will benefit the company? Will your management allow you time to work on improving it? If they are not familiar with Six Sigma, they may not provide any emphasis for you to work on it using Six Sigma. But you could still follow the DMAIC methodology and the appropriate tools to make the right conclusions and recommendations on your own. But, what is important is that they agree with your recommendations and implement your project findings so that you can track improvements and report progress and benefits. When you submit this project for certification, we would validate that you have followed the right approach/methodology. You will have to get a letter from the sponsor stating that this project is complete and that recommendations have been implemented. Hope this helps. Best Regards, SJ

Hi Sreejit, Can you try some sort of an Attribute Measurement Systems Analysis (MSA) to determine if people are correctly interpretting the questions? If your scores on MSA (Kappa values or percentage agreement) are low, you could redesign the questions and try it again until people are correctly interpretting the survey form. SJ> PS: This is an advanced topic that should be posted in the private benchmark six sigma forum.

Dear Mohit, The Sigma level can be computed based on the number of defects per million opportunities (DPMO). DPMO = (Number of defects)*1000000/(Number of units)/(Number of opportunities for defects per unit) The number of defects and number of units can be uniquely determined. However, there is no unique way to determine the number of opportunities for defects per unit (OFE). As a result, there is no unique number for DPMO and hence Sigma Level. This may sound counter intuitive that Sigma Level can be any value that the user wants it to be - by manipulating the OFE. The main objective of the Six Sigma project should be to capture the baseline Sigma level before the project and then use the same definition of OFE when calculating the Sigma level after the completion of the project to show an improvement. Let's look at the airline example, I had used a value of OFE = 1, which is each flight can have one opportunity for error (crash). This gave a Sigma level of 6.3. However, we could also have chosen the number of miles travelled by the plane as OFE. If on an average, a plane travels 1000 miles per trip, then we would get: DPMO = 36/(52.6*1000) = 6.8 x 10^(-4) This corresponds to Sigma Level of 7.6 (including the 1.5 Sigma Shift). Of course, if someone assumes that the opportunity for error is defined as every second of plane travel there is an opportunity of a plane crash, then we would get an even higher Sigma level! Hope this helps, SJ>

Dear Shyamal, When the population size is small, we usually find that we end up having to sample a relatively large percentage of the population. Sampling is very effective when the populations we are dealing with are very large. SJ>