How to pass the ASQ Six Sigma Black Belt exam

Well, ok, the article title is a bit misleading. This post is moreso about how I passed the ASQ Certified Six Sigma Black Belt Exam (on the first try!) - but it may give you some tips that will help you. So first off, let me give you some background about my experience so it'll give you an idea of what I started with. I took a Six Sigma Black Belt course in college but that was ten years ago. I still managed to keep some of the notes from the class which helped a little bit. After college, I got green belt certification at my first company and did a couple projects. Since then, I've been doing black belt level projects sporadically with my current company. Lean has been a greater focus in my role and six sigma is more like a nice-to-have skill. I thought it would be important to round out my skill set as a problem solver and get ASQ certified.

I first submitted a few projects I did to ASQ in order to sit for the exam - my projects were approved and I had about 3 1/2 months to study. The first thing I did was a quick search online through some blogs and forums to get some exam advice. The most useful article I found was from Nicole at a blog called Quality and Innovation (article can be found here). Based on advice from her blog, I bought two books - the CSSBB Primer from the Quality Council of Indiana and The Certified Six Sigma Black Belt Handbook (Second Edition) by Kubiak & Benbow. I bought a used copy of the Handbook off of Amazon that included the CD. The handbook arrived first around 2 months from the exam date. I started reading it from page 1 and to be honest found the content structure to be a bit confusing. I understand what they were trying to do with tying to the Body of Knowledge but for me it just seemed cumbersome. The CD contained one file and it was a 70 question practice exam (one that I later found online for free also). The handbook did end up helping me on exam day though as I was able to find a couple of key definitional points in there that weren't in the Primer.

When the primer (along with the Solutions handbook and test CD) came, I started going through each section one at a time. After each section, there is a set of blue pages that has practice questions related to that material. I found those questions to be very useful in testing knowledge of the content. The structure of the questions were also very similar to the ones found on the actual exam. I took about three weeks and two hours each day to walk through the entire primer and every blue page test question. The solution handbook explanations of the questions were very detailed and well-written. In the last 8-10 days before the exam, I started working through the test CD. The test CD has a ton more questions and you can do them either as simulated exams or topic by topic. I chose to do a bit of both. The questions and answers on the CD are actually explained very well also and they reference back to the primer with exact pages.

The test, as you probably know already, is open book and open notes. You can't bring in the blue page question sections so you have to rip those out of the primer. So what exactly did I bring with me on exam day?
  1. My notes - As I went through the blue page test questions and the CD questions, I jotted down notes on all the questions I got wrong - those notes helped me a lot in the exam.
  2. The CSSBB Primer - I ripped the appendices out of the back and laid them on the table to make them easier to reference during the exam. I probably went to the primer about fifteen times during the exam.
  3. The Kubiak and Benbow handbook - again, I think I referenced this twice during the test.
  4. Calculator - my TI-83 wasn't allowed so I brought an old Casio.
  5. Two bottles of water (long test!)
  6. Four #2 pencils (I only used one)
So on exam day, my strategy was to circle all my answers in the exam book and then to transfer them to the Scantron at the very end. This strategy nearly backfired on me because I was literally filling in my bubbles in the final minute of the exam. I probably cut it a bit closer than I should have! In comparison to the practice questions, I found the exam to be equal in difficulty on the non-statistics questions but a little easier on the ones where I actually had to bust out a calculator. I left the room feeling relatively confident that I passed the test although theres always that little voice in the back of your head that questions that confidence! The ASQ site says you typically get results in about 7-10 days - I took my test on a Saturday and got my results the following Friday so about 6 days. They send you an email first and then a packet comes in the mail with your shiny certificate. Anyways, I hope the story of my journey has helped you a bit - let me know if you have any questions!

Little's Law - Application in Lean

John Little
John Little - MIT Professor
I was recently teaching some value stream mapping concepts to some lean leaders and we were talking about the relationship between WIP and Lead Time. I shared with them the important concept of Little’s Law in relation to lean manufacturing. Little’s Law is most commonly used by service organizations to explore wait and response times. To paraphrase the Little’s Law Wikipedia page a bit, Little’s Law is that “Average # of customers in a stable system L is equal to average arrival rate λ multiplied by the average time a customer spends in the system W”. Relating this to a mathematical formula yields L = λW.

Well how does this relate to manufacturing and value streams? If we break down the statements in the definition and relate them to lean terms, then this relationship can be easily understood.

“Average # of customers in a stable system L”: In a service organization, Average # of customers in a stable system is essentially system WIP. In a value stream map that would be the parts in the system. A stable system in service would describe any time there isn’t a built in ramp up and ramp down like opening time and closing time perhaps. A stable system in value stream mapping would be similar – any time you are in normal production and not new production introduction. In our new formula we’ll define L = WIP

“Average arrival rate λ”: How often a customer walks into a service process is your arrival rate – well what would that be in lean? How often should parts arrive into a value stream – theoretically at the customer demand rate. The customer demand rate we will call throughput which will be a measure of units over time (e.g 2 parts per day, 1 part per week, etc). For our new formula, λ = T (throughput).

“Average time a customer spends in the system W”: For a service organization this is exactly what it sounds like – basically how long he/she waits for a response. If its McDonalds it’s the time from when the customer walks in to when they order food and leave the queue. Relating this back to manufacturing, if our customers are our WIP, then we can think about how long the WIP is in our system. This is of course leadtime! So for our new formula W = LT (leadtime)

So after breaking down Little’s Law we now have a modified formula for manufacturing and value streams: WIP = T x LT. So the inventory in your value stream is a function of throughput times the leadtime. This is a very powerful relationship to understand and can prove useful in many situations. My boss recently told me that my inventory needed to be no more than $1.2m on a critical value stream. By knowing the average value of a part in the value stream, I could tell that this represented approximately 30 pieces of WIP. I knew based on required customer demand that throughput was 2 per day. So:
Target WIP = 30 pieces
Throughput = 2 per day
Lead Time = ?
30 = 2 * LT
LT = 15 days
So based on this, I know my target leadtime is now 15 days. I know based on system actuals that my current leadtime is 18.5 days. Based on this knowledge I know how much of a leadtime improvement I need to make in order to achieve my bosse's targets. Little's Law is also useful in doing sanity checks while doing value stream mapping.
Any thoughts about Little's Law and experience applying it to manufacturing situations?

Healthcare Kamishibai - Kaiser

I was recently shown this neat little Kamishibai system in a Kaiser hospital. It shows all the things a new mother has to do after giving birth before going home. One side shows the necessary task and the other side shows a check mark indicating completion. This is a great example of lean applied in the healthcare sector.

The 5S's - Squid Salami Stopwatch, Sasquatch, Salmonella?

Love this video from Mark Graban's ( Youtube channel (link if the embedded doesn't work:

It really does hold true though. How many times have you walked through the office area of a factory and seen someone with their desk taped off and labels everywhere. I'm not saying office organization isn't important, but you can defnitely go too far. Lean in the office is about streamlining processes using tools like four-field mapping not about putting tape around pencils!

Have you ever seen office 5S gone wrong?

Hoshin Kanri in the lean business

I've recently been helping an Aerospace site build the Hoshin Kanri tool into their business strategy. When we first started I hadn't used Hoshin Kanri a lot so I decided to do some reading. My co-workers had recommended a couple books but I found these really useful (both available from Amazon)

The Hoshin Kanri Memory Jogger by Joseph Colletti - It has memory jogger in the title but this book provides quite a good overview of Hoshin Kanri. Well-illustrated.
Hoshin Kanri for the Lean Enterprise by Thomas Jackson - Shingo Prize winner and very specific focus on Lean Enterprise.

After doing some reading, I felt more comfortable with the deployment. First step was training the site steering committee and this was done over the course of a 4 hour session.  Next we sat down and tried to determine our site vision. To do that we had to be introspective on where we stood in terms of a long term lean strategy. After assessing our current state we came up with a single statement that now stands as the vision for our business. This wasn't a 'lean' vision either - this was our company's vision. Hoshin Kanri isn't just about lean - it should be a continuous improvement planning tool ingrained in all aspects of the business. 

After establishing our vision, we built a list of long term goals for our business. These were 5-year targets for the site with a focus on safety, quality, delivery and cost. We limited ourselves to six targets to avoid over complicating our first X-Matrix. 

The long term goals led to a list of annual objectives. We focused on making the annual objectives SMART (Specific, Measurable, Attainable, Relevant and Time-Bound). For the annual objectives, we limited ourselves to ten and these came straight from the long term goals. Example: Reduce inventory from 10m to 8.8m by Dec 2014. 

From the annual objectives we brainstormed a list of macro projects that would help us get to the desired targets. These projects formed the basis of our site CI plan. Our plan is track these projects monthly measuring ourselves against our key business metrics and then to adjust based on our progress (PDCA!). 

So far, the Hoshin Kanri process has been helpful in keeping the teams focus on the CI Plan. Seeing the linkage of projects to the measures and the annual/long term objectives lets the leadership team see the bigger picture.

We're in the infant stages of Hoshin planning and we still need to work on linking the divisional plan with the site plan and then down to the functional plans but that's part of the journey. 

What are your experiences with Hoshin? Have you found it to be a useful structure?

My New Year's Resolution

With my new job I didn't get to spend as much time as I would have liked on my blog. My resolution for 2014 is definitely to write more, read more, listen to more webcasts and attend a few seminars. The learning never ends with lean!