## Top 10 Statistics Topics for the Six Sigma Black Belt (CSSBB) Exam

Image Credit: Doug Buckley (http://hyperactive.to)

[IMPORTANT NOTE! As of April 20, 2015 I now have a NEW FAVORITE introductory statistics textbook… the one I’ve always dreamed of having, but it just never existed before. But today it does!! <3]

Not too long ago, Darrah Turman from New Jersey contacted me for some additional insight into preparing for the ASQ Certified Six Sigma Black Belt (CSSBB) exam. He’s taking it in March, and like many prospective Black Belts, he’s most concerned about the statistics parts of the exam… it’s been many years since he’s had a statistics course.

As a result, I’m going to start a series of blog posts over the next two weeks that you can follow along with if you’re busily getting ready for your exam. Today, we’ll start with one of Darrah’s questions: How do I focus on the right statistics? I’ve decided to post my “Top 10 Statistics Topics” that seem to be featured heavily in Six Sigma.

Here are My Top 10 Six Sigma Statistics Topics!

1. Central Limit Theorem – This is the magic that serves as the foundation for so much of what quality professionals practice. In short, whenever you take many samples for which you have a sum or an average value that you’ve computed over that sample, the distribution of the whole collection of sums or means is going to be normal!! This is why when we’re spot checking parts or products in quality control, we take batch averages and know they’re going to be distributed normally. Find out more here!
2. Know Your Distributions! – Distributions come in many shapes and sizes, and you should be familiar with how to describe and characterize them (also, be able to recognize their equations). Continuous, discrete, normal, Poisson, binomial, hypergeometric, exponential, Weibull, uniform, symmetric, unimodal, bimodal… you should be familiar with all the words that describe distributions.
3. Know Your Inference Tests! – It’s helpful to have a general sense of which inference test is appropriate for which kind of problem. For example, if you’re trying to figure out whether two categorical variables are independent, that’s a Chi square test of independence. If you’re trying to figure out whether a mean matches a particular standard, target, or recommended value, that’s a one-sample t-test. As part of knowing your inference tests, you should know what the form of the null hypothesis is for each test, as well as the form for each incarnation of the alternative hypothesis (there will be between one and three of them for each test).
4. Type I, Type II, and Power Analysis[Book Chapter + PPT] – If you’re planning a statistical inference test, it’s important to know how big a sample size you need so that your results will be statistically significant, and you’ll also need to balance the trade-offs between the different types of errors you can encounter. This chapter will help you do all that.
5. Computing Confidence Intervals – Just by knowing the average and standard deviation of a small sample size, you can use the Student’s t distribution to quickly and easily compute a confidence interval, because all confidence intervals come in the form Estimate +/- Margin of Error. The most complex part is learning how to look up the t value for the appropriate confidence interval size, and degrees of freedom. (Confused as to whether you should use the normal distribution or the t distribution? Don’t be… always use the t distribution. As your sample size gets bigger and bigger, the shape of the t distribution will get more and more like the shape of the corresponding normal distribution, until they are exactly the same.)
6. Using the Normal Model to Find Areas Under the Curve[Book Chapter + PPT] – It’s really good to be familiar with z-score problems. In addition to making you more comfortable with the normal model, it’s a useful technique for finding the probability of observing values in a particular range.
7. Understanding Scatterplots, Correlation Coefficient (r), and Coefficient of Determination (R2) – Scatterplots help us see the relationship between values of two quantitative variables. Correlation tells us how much scatter is in the data, and the coefficient of determination tells us what proportion of the variability in the data is explained by a (typically linear) model.
8. Process Capability Problems – You should be able to tell the difference between your Cp’s and Cpk’s, and perform basic calculations. Also know that if your data is not normal, you’re going to have to use some kind of data transformation before you determine process capability.
9. Know Your Control Charts! – There are many different incarnations of control charts. You should be able to distinguish your variables from your attributes, and understand when to apply the various kinds of control chart (along with basic calculations).
10. Logit-Probit & Odds Ratios – These models help you deal with situations where there is a binary response variable. Basic familiarity with what the regression models do, and how to calculate odds, should be a part of your study plan.

Enjoy! Check back for more chapters throughout February 2015.

## Type I Error, Type II Error, and Power Analysis in R

Image Credit: Doug Buckley of http://hyperactive.to

At some point in the life of most quality engineers, quality managers, and Six Sigma Black Belts and practitioners — you will have to compute an appropriate sample size to ensure that the results from your study will be statistically significant. To achieve this, you might have to perform a power analysis (which I know sounds really scary, but it doesn’t have to be).

Here’s the powerpoint and R exercise that I use in my classes to compute sample sizes, perform power analysis, and plot power curves to help me choose the most appropriate sample sizes. Feel free to use, reproduce, recreate, etc. — just please use appropriate attributions and let me know if this is helpful to you!

Nicole

Radziwill-type-i-ii-power-effect (Powerpoint Discussion of Type I/II/Power)

power-sample-size-75-925 (R Exercise to Compute Sample Sizes and Plot Power Curves)

## Cramming for Your Six Sigma Black Belt Exam?

Nervous about your Six Sigma exam?

Are you making last minute preparations for your ASQ Certified Six Sigma Black Belt (CSSBB) exam? If so, you’re probably reviewing your notes, hoping that you’re bringing all the right stuff in with you. When I passed my CSSBB on the first attempt, I found that I had GREAT notes with me, and I’d like to share them with you!!

Radziwill_CSSBBNotes_1

Radziwill_CSSBBNotes_2

The attached PDFs contain PRECISELY what I carried with me into the exam, along with a few books and a handful of good habits and good luck charms.

[IMPORTANT NOTE! As of April 20, 2015 I now have a NEW FAVORITE introductory statistics textbook… the one I’ve always dreamed of having, but it just never existed before. But today it does!! <3]

[Note: On February 9, 2015 I also added my Top 10 Statistics Topics for the CSSBB Exam to this blog]

GOOD LUCK! 🙂

## Should You Get Your Six Sigma Black Belt (SSBB) from ASQ?

A couple of weeks ago, I got this email:

Comment: I am basker from NJ, and I have a PMP certification, I want to get a six sigma black belt certification — are there other certifications out there other than one from ASQ ? that you would suggest and what is the cheapest and quickest way to pass the black belt certification ?

Kind Regards,

Basker.

Basker would like to know the quickest and cheapest way to get a Black Belt certification. Here are the routes I know about to obtain the certification: 1) you could go to http://sixsigmaonline.org, whose training and certification program costs about \$1000, 2) you could attend the 4-week program offered by http://www.6sigma.us which runs about \$8000, 3) you could go to Villanova and pay \$7000 for their three-course package, or 4) you can study on your own, complete two projects and get a Project Champion to sign an affidavit, become an ASQ member and pay \$299 to take the exam, or don’t become an ASQ member and pay \$449 to take the exam.

The ASQ option is probably the quickest and cheapest if you’re good at self study, and dedicated to the task of Six Sigma problem solving. However, with the ASQ certification you also get a lot of clout. I don’t think any other organization has more than 10,000 Black Belts supporting the program, working on updates to the new exams, and keeping the curriculum current. I just personally think it’s a much more viable Black Belt designation than the other programs.

I also asked Jeanine Becker, who works at ASQ in Milwaukee and is responsible for the Six Sigma Forum, what she thought. Jeanine says:

ASQ certification is a formal recognition by ASQ that an individual has demonstrated a proficiency within, and comprehension of, a specific body of knowledge. Nearly 150,000 certifications have been issued to dedicated professionals worldwide.

Anyone can give you a “certificate” for simply attending a course, but an ASQ certification is the recognized gold standard for certification for quality professionals.  ASQ is the only third-party provider of certifications for the quality professional.   Those that are ASQ certified have the potential to earn a higher salary than their counterparts.    The majority of positions companies recruit for that require certifications specify an ASQ certification.

I totally agree. And as a result, Basker, I’d say go with the ASQ cert.

Nicole

## How I Passed My ASQ Certified Six Sigma Black Belt (CSSBB) Exam

I very recently took my ASQ CSSBB exam and passed! Here’s what I think helped me:

[Note: On February 9, 2015 I added my Top 10 Statistics Topics for the CSSBB Exam to this blog]

1. I studied for about 4 weeks (2 weeks very gently, 1 week much-more-work-because-the-exam-is-getting-closer, and 1 week of panicked, freaked out all nighters) using

2. I took about 10 pages of really good, concise notes. (I’ll share those with you sometime before the end of the year… want to write them up for public consumption.) (Note from October 4, 2012: OK, so I didn’t package them for public consumption, but I did post PDFs of EXACTLY what I brought in with me to the exam.)

3. I brought about 15 super sharp #2 pencils just in case 14 of them broke. I made sure all the pencils actually SAID #2 on them, so the Scantron machine wouldn’t fail me.

4. I brought my SMART RULER. I’ve had this ruler since the late 1980’s, and every time I’ve taken a tough test, I’ve had my smart ruler with me in case I need to underline anything, or draw dividers between notes. I usually never have to USE the ruler. Usually, its presence is enough to make me do better on any exam.

5. They (the people who say such things) say that peppermint makes you smarter. So I got a new pack of Orbit peppermint gum and chewed it like I had obsessive compulsive disorder for all four hours. (Afterwards I found out that the peppermint thing isn’t really backed up by research, but I didn’t know that going into the exam, so I believed that the peppermint would make my brain work better, and that belief probably helped me out. Got to stack the deck in my favor… didn’t want those 4 weeks of studying NOT to pay off.)

6. When I wasn’t chewing gum, I was nibbling on a Reese’s peanut butter bar. Best 300 calorie investment ever made… the protein made my stomach stop growling so it wouldn’t bother the other test takers.

7. I also brought a couple very cold Diet Cokes, to wash down the peanut butter and the gum taste.

8. To appropriately address my superstitious nature, I wore my Ganesh necklace. In Hindu parlance, Ganesh helps break through obstacles, and I figured the exam that stood between me and CSSBB-hood was definitely an obstacle I wanted broken. (Hey, whatever works, right??)

🙂

Nicole

## How to Pass Your ASQ Certified Six Sigma Black Belt (CSSBB) Exam

[IMPORTANT NOTE! As of April 20, 2015 I now have a NEW FAVORITE introductory statistics textbook… the one I’ve always dreamed of having, but it just never existed before. But today it does!! <3]

[Note: On February 9, 2015 I added my Top 10 Statistics Topics for the CSSBB Exam]

[Note: On October 4, 2012 I posted the notes I brought into the exam. You might want to check them out.]

* * * * * * * *

(Or more appropriately maybe… how I did it, and what I wish someone had blogged about before I sat for the exam! This is the chronicle of my CSSBB experience.)

I just took my ASQ Six Sigma Black Belt (CSSBB) exam… and PASSED! On the FIRST TRY!! (My reaction upon hearing the news was… “I am a statistics NINJA!!!” A very academic friend corrected me, and said no – not quite – the CSSBB is more like a learner’s permit for a PhD in statistics. OK, that’s cool too.)

My intent in this post is to share with you what I believe helped me get through this very daunting 150-question, 4-hour, heavy-on-the-math multiple choice exam. (Relevant superstitions and helpful snacks are described elsewhere.) This was a particular achievement for me, because although I had been doing small scale Six Sigma projects for several years, I originally intended to take the exam in the fall of 2008… and just didn’t get around to it. I had, at that time, recently completed a couple of doctoral level statistics courses and so I felt super powerfully capable at the time. But what inevitably happens is that as the days go by, and you don’t use the knowledge for practical problem solving, you get rusty and you forget.

Fast forward three years, to the fall of 2011.

When I took the plunge and signed up for one of the most recent offerings of the exam, I knew I had a lot of ground to re-cover before sitting to take the test. I knew I’d have to order some books or flashcards and spend a lot of quality time with them. I knew I’d have to refresh my memory on the nooks and crannies of all those statistical tests, especially the ones that are most frequently used in manufacturing situations. So my first step was to search Google to see if anyone had posted their personal experiences studying for – and hopefully succeeding with – the ASQ CSSBB exam.

I wanted to know: What resources helped? What resources didn’t help? What books were the most useful references to you as you were studying? Are the flashcards useful? I searched and searched all over the web, but couldn’t find any useful advice. I used search terms like “cssbb advice,” “how I passed my Six Sigma Black Belt exam,” “best resources for the Six Sigma Black Belt exam” and “best study guides for the Six Sigma Black Belt exam.” No luck. Everything led me back to companies trying to sell their training sessions. I didn’t want a training session… I wanted practical, free advice from someone who had been in my shoes not too much earlier than me.

So here it is! Feel free to post some comments if any of this advice is helpful, or if you want to add information about what you found useful when you were studying. (Remember, personal experiences with CSSBB prep are hard to find on the web, so anything you contribute is bound to be helpful to people who are actively preparing to be certified.)

#1 CSSBB Primer from the Quality Council of Indianahttp://www.qualitycouncil.com/cssbb_p.asp

BEST. Book. Ever. I ordered the CSSBB Primer as well as the CD with the practice exam questions, and although I was daunted by the sheer heft of the book, the large fonts make this reference a pleasure to get to know. It feels like someone is giving you all the essential knowledge you need for the exam, along with a cookie, a glass of milk, a hug, and a heartfelt “you can do it!!”

I read through the entire book, underlined definitions or phrases that I thought were important, and used post-it notes to tab topics that I thought I’d want easy access to during the exam.

Do ALL the questions in the blue part of the CSSBB Primer. It will take time… for me, it took about 3 weeks, working on about 10 to 20 questions a day. Understand not only what the right answer is for each question, but also WHY THE OTHER OPTIONS ARE WRONG. You won’t be able to take any of the blue pages into the exam with you, so make sure you take notes about the key facts, formulas, or techniques when you have “a-ha” moments doing the practice problems. YOU WILL NOT REGRET IT.

The real ASQ CSSBB exam is actually EASIER than the questions in the CSSBB Primer, but the question styles and formats are very similar. The reason that the real exam is easier is that there are a lot of questions in the Primer where at least two of the multiple choice options will tempt you into believing that they are both correct. The multiple choice options on the real exam seem to be much more distinct – that is, you’ll have an easier time distinguishing why the wrong ones are wrong.

I think the number one reason that I passed the exam was because of the time I spent on the practice exam questions in the CSSBB Primer. The practice questions on the CD were useful too, but I think the ones in the book were the most useful.

#2 (NEW) Statistics (The Easier Way) With R by Me (Nicole)

SECOND BEST BOOK EVER. Disclaimer: I am biased.

In 2014, I wrote the book that I wish had been written previously… to help people understand the fundamental statistical concepts that you NEED to know before the more advanced Six Sigma concepts. Although I did not take this book with me into my CSSBB exam in 2012, I did take the NOTES that became this book 🙂

#2 (OLD)  The Certified Six Sigma Black Belt Handbook, Second Edition by Kubiak & Benbow

This is the second book I took with me into the CSSBB exam.

This book has mixed reviews on Amazon because apparently the book made it into print with a bunch of calculation errors in it. I didn’t lean on the calculations in this book, though, because I had the CSSBB Primer for that – and as a result, I thought this book was a great reference. Some of the concepts aren’t covered in enough depth, e.g. TPM, but there were several problems on the real exam that I wanted to double check in the references before I shaded that scantron circle with my #2… and this was the book that helped out the most in that regard.

#3  An Introduction to Statistical Methods and Data Analysis by Ott & Longnecker

This was the third book I took with me into the CSSBB exam, and I think I needed it for 3 questions, 2 of which had to do with arcane aspects of DOE. However, it’s also the book that helped me get all my hypothesis testing straight, AND understand the assumptions for all of those tests.

I also LOVE LOVE LOVE this book, and think it should be a required book on the bookshelf of every Six Sigma aficionado out there.  I was first introduced to this awesome, awesome book as a student in STAT 451 at Penn State… an upper level applied stats class (which I believe is now STAT 460). In addition to providing great explanations of the concepts, Ott presents every statistical test as a recipe… what assumptions to check, how to set up the null and alternative hypotheses, how to calculate the test statistic, and how to interpret the calculated and critical values of the test statistic depending upon what alternative hypothesis you selected.

I have a hard time trying to remember whether your calculated test statistic has to be greater than or less than the critical value that you look up in a table… and this is the reference that helped me keep all those important details straight.

This book is expensive, but it’s worth it. If you can find an earlier version, these are usually much more affordable and JUST AS GOOD. Thank you, R. Lyman Ott, for making me love statistics, want to use statistical tests all the time, and want to teach college students how to do it too. You have been one of the most influential people in my life.

#4 Six Sigma for the Next Millennium: A CSSBB Guidebook by Kim Pries

I really tried to like this book, but it’s big, heavy, and there is a lot of whitespace on many of the pages (very unlike the CSSBB Primer). The amount of information per pound is relatively low. HOWEVER, I like the way it consolidates notes by topic with one topic per page. For example, there is one page with Deming’s 14 points. There’s one great page on Project Scope and another great page on Scope Containment Ideas. I’m definitely going to use some of the one-sheeters for teaching my statistics and quality classes.

Unfortunately, the book just didn’t help me as I was studying for the certification exam.

#5 The Six Sigma Handbook, Third Edition by Pyzdek & Keller

Great book but HARD TO FIND STUFF QUICKLY. I’d say read this before your exam instead of bedtime stories, take it with you when you lay on the beach, bring it to the coffee shop while you’re gently relaxing over synthesizing your Six Sigma knowledge into your blood and muscles. This is an excellent book for getting a deeper, more thoughtful understanding of Six Sigma related topics, but was not one I chose to bring into the exam with me.

#6 Statistics for Six Sigma Made Easy by Warren Brussee

This was the LEAST useful book to me for my exam prep (but it might just be as result of how my brain is wired). I find that whenever an author writes very conversationally, trying to simplify the concepts by writing long explanations of the topics (as if he or she were sitting there with you trying to explain them to you), it just confuses me. I need recipes, like what Ott provides in his book.

I can definitely see how this book might help you if you’re totally new to statistics, or if you’re starting off on the path to becoming a Six Sigma Green Belt, or if you just need someone to explain to you what in the world the meaning is behind these statistical tests.

However, IF YOU’RE CLOSE TO BECOMING A BLACK BELT, you should have a lot of this material under yours already. As a studying resource, Brussee’s book won’t be as useful to you.

Hope this helps! If you have any questions, please post them as comments below, and I will try to respond to all.