Top 33 Six Sigma Interview Questions and Answers

When we think about a job interview, many questions come to our mind. How will we deal with it? Is it going to be tough? Sometimes it seems tougher than doing the job itself, and when the interview is a technical one, we will have many questions piled up in our mind. At this point, we must know that the main thing which does matter during the interview is not only knowledge but our confidence and our outlook towards the interview questions. Sometimes, we might not know the answer, but that’s fine. No one knows everything!

We must try to answer all the questions which we are confident about. One must also accept it as a fact if they are not sure about some questions. While going for an interview for a Six Sigma role, the questions depend on the professional level for which you are seeking the job, that is, if it is Green Belt or Black Belt.

The first question any interviewer would ask is “tell me about yourself?”  Here, while describing yourself, you must describe the previous work experience, achievements and the projects that you have worked in.

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All the remaining questions will depend upon how you explain your profile to the interviewer. They will now start questioning you based on whether you are a Six Sigma aspirant, an expert or a seasoned six sigma professional. To answer these questions,  you should first have a clear idea about the below three questions:

Q1. What is Six Sigma?

This can be answered in many ways, you can either give the description of metrics (3.4 defects per million opportunities) or methodology DMAIC, DMADV and DFSS or one can explain the 6 times standard deviation that fits at one side between the mean value and customer specification limits.

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Q2. Why Six Sigma?

The interviewer wants to know if you have ever tried to think about why only Six Sigma and not beyond. You should analyze the answer to this question by yourself, why 6 why not 7, not 5?  Here we can say that while achieving the Six Sigma, the yield would be 99.9996%, which is hard to achieve otherwise as we need to commit to only 3.4 defects, the target must be difficult and achievable and therefore it is Six Sigma.

Q3. Have you completed any projects?

For this question, you must describe the projects which you really worked upon and you have very good insight into. This is very important as the answer to this question will decide the direction in which the rest of your interview goes.

Now the next few questions would be based on your project, for example:

Q4. How did you decide on the projects and what were the issues?

Here you must mention about the VOC or VOP. The VOC could be given by the clients or customers by reactive feedback or by conducting the survey or the customer's ratings to the process. Through this, we find the criteria as customer's dissatisfactions towards the products or services.

Next, there would be questions based on the Define Phase, some of these are:

Q5. What was the project scope?

The project scope makes the boundaries for the project so that people should be the focus on the inside of the boundary and anything beyond boundary is not questionable for the projects. Boundaries can be limited to one process, location, people and time durations.

Q6. How did you set the goal of these projects?

The project goals should be the basis for the SMART approach, which we could see by the confidence interval. How the process is behaving.

Q7. How would you decide the project level, whether it should be a Black Belt or a Green Belt project?

These things depend upon the benefits we would get after the projects and the area of projects. If the scope of the project is at the company level, it should be counted as a  Black belt project. However, if it is limited to one single process, it would be considered as a Green Belt project.

Q8. What would you do after getting the VOC/VOP?

Once we receive the customer complaints and Voice of the process, we need to make a Critical to Quality check which helps us to change the voice of customers into the metrics. Six Sigma would work on practical problems and change them to statistical problems with statically generated solutions.

Q9. What is SIPOC?

It is the tool used to see the overall process at one instant, it gives the whole picture of Suppliers, Inputs, Process, Output, and Customers.

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Q10. What are the Milestones?

In Six Sigma process, it depends upon the methodology, either DMAIC or DMADV, and for each stage, there should be some time durations involved, the milestones provide the time duration limit for each stage, if we extend the time limits, we need the approval from stakeholders.

Q11. What is the ARMI or RASIC?

With the help of ARMI or RASIC, the whole Six Sigma team comes to know that who the authorized person is, who is responsible for the project, who should be a consultant and who should be informed so that there are no conflicts at work.

Q12. How should we define the problem statement?

The problem should be clear and crisp and should be defined in metrics so that it is easier to make the stakeholders understand what would happen if the problem has not been resolved, the future consequences also should be shared with stakeholders.

Q13. How to collect the data?

First, we should be clear about the Y = F(x), by this we should be clear what all factors are impacting on Y, and accordingly, we must plan of data collection, which should be stratified.

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Q14. What are the types of data?

Data can be of two major types – Quantitative and Qualitative. Under the quantitative data comes the  Continuous data and Discrete data attributed comes under the qualitative data category. This can be described in a more detailed manner.

Q15. What is MSA?

MSA is Measurement System Analysis, using this we see whether our measurement system is correct or not. For service industries, we do the Attribute analysis.

Q16. What is Gauge R & R?

In Gauge R and R, we gauge by repeatability and reproducibility. Here you need to describe the difference between the repeatability and reproducibility.

Q17. What is the Normal distribution? If the data is not normal, what should be the next step?

In Normal distribution, we see the p-value, and if it is not normal, we try to make it normal or transfer into the Box-Cox transformation.

Q18. What is Process Capability and difference between Cp and Cpk?

Here we need to give the whole information about the process and their capability with some real time examples. Also, describe the difference and benefits of Cpk and can we not use the Cp.

Q19. What is the Value Stream Mapping?

Describe the VSM and here questions could be asked the difference between the process map and VSM. In this, they could ask about the cycle time, takt time, lead time. Hence, we need to be very clear of all those times.

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Q20. What is the Ishikawa diagram?

The Ishikawa diagram is also called the cause and effect diagram or fishbone diagram. After the brainstorming session, we use this to segregate all the issues in 6 Ms (manufacturing) and 4 Ps (service industries).

Q21. What is Pareto chart?

Pareto is the most used tool in six sigma and quality. Here you must describe the Pareto analysis to prioritize the issues, or causes and define each and every aspect of the Pareto chart. How many data points are needed for Pareto? what if Pareto ratio 50:50? So by all this, we mean to say that we must be clear about each aspect of Pareto.

Next, we will move to the hypothesis testing as this is the most critical part. Here we need to see, what all the hypothesis tests we have done, and why only those tests? what was the significance of these tests? When do we need to do regression? When do we Chi-square tests? This should be clear and we need to give the whole information with our testing results and what has been observed in the tests. Some more questions associated with Hypothesis testing can be:

Q22. What is Alpha and Beta risk or what is the P value?

Before you go to explain about the alpha and beta risk, one should know what is H0 and Ha, H0 is acceptable when we have p-value more than 0.05 or 5%. And if it is lesser, we accept Ha. And sometimes, what we accept or reject could be wrong assumptions, that time we are on risk, which could be alpha and beta risk. And p-value is the probability, when we are at 95% confidence with our sample, then we are at 5% of risk chances or probability. And if the p-value is more than 5%, that time we go as per H0, since risk at higher side, however, if the p-value is lesser than 5%, we are happy to take the risk and accept Ha. Hence, it can be very clear when doing we at these risks, what all the consequences of having these risks.

Q23. What is the difference between the R SQR and R SQR adjusted?

These are the part of regression testing, and one must know the actual reason to see the R SQR and R SQR adjusted.

Q24. What is an affinity diagram?

Here we do the clustering after the brainstorming sessions. We would get to know where we need to keep all inputs received by the team members.

Q25. If the data is non-normal, what hypothesis test should we do?

If the data is non-normal, we need to try to make data normal, if we cannot, then we need to use the non-normal hypothesis testing, as per their subgroup size.

After the analyze phase, questions can be asked about what improvement plans you made, or the tools used. The improvement can be done using the FMEA, therefore we should know what is FMEA and what are the types of FMEA, what is RPN value and how to calculate it. We can also use the affinity diagram for the solution purpose, which can be done by brainstorming to resolve the issues.

Q26. What hypothesis test we can do in improve phase?

In the improve phase we do the 2 samples testing to see the before and after effect. Therefore, we should know what all hypothesis tests we can do in improve phase.

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Some questions on Control Phase:

Q27. How and Why control is required?

Control needs to be done once the improvement is sustained. Control is usually done after the project completion so that there are no prevailing issues.

Q28. What are the types of control charts?

We must give information about all control charts which we use for continuous data and discrete data.

Q29. What are the rules for control charts?

Here we must give the details for control charts and all the rules, which we can see in Minitab and Nelson's rule.

Apart from these questions, they may ask a few more questions to check your six-sigma knowledge, like:

Q30. What is the difference between the Histogram and Box plot?

Though both of them give the same information, their usages are different. These are used for continuous data.

Q31. What is the difference between the control and run chart?

Here we must know the difference between them both and we must also know the characteristics of the run chart and control charts.

Q32. What is the difference between specification limits and control limits?

Control limits are process driven. It refers to the real-time value that the process is operating on. Whereas, the specification limit is given by the client and the process targets are set by the client based on market performance.

Q33. While starting a Six Sigma project, what do we need to see first?

First, we need to see that process is in control or not (stability), and if data is normal or not, if the process is not stable, we cannot run the project, we need to make process stable, then we need to see the process normality, as per the process normality/non-normality we do the process capability to see whether the process is capable enough to run the project.

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Here, we have tried to cover all the questionnaires, which are usually asked during the interview, however, these are not limited to, six-sigma as it is a vast subject, and any question can be asked. We need to know each and every aspect of Six Sigma projects and lean concepts. Here we have only covered the questions related to six sigma however, questions could be asked about Lean management as well.

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Urvashi Chitranshi