Six Sigma Black Belt

Given below are some of the important interview questions on Six Sigma Black Belt (SSBB) asked by interviewers. Checkout them if you are looking for a job in Quality Management.

Q.1 Differentiate amongst DMAIC and DMADV
Both DMAIC and DMADV are different, as DMADV is proactive approach for preventing defects and focuses on the design process, DMAIC is reactive approach for reducing defects and focusing on the current process.
Q.2 Explain the DMAIC methodology
DMAIC expands to various phases of six sigma as: define (identify the Y and X), measure (measure the X and Y and prioritize the Xs), analyze (Test XY relationship), improve (improve the Y and crucial Xs), and control (monitor Ys and crucial Xs)
Q.3 What are a Core Business processes?
Core business processes refer to the organizational processes which are vital for value creation in the company.
Q.4 What is value in Lean?
The value in Lean is the level of fulfilling a customer's requirement by the product or service.
Q.5 What do you understand by Value Stream in Six sigma black belt?
The Value Stream in Six sigma black belt is actually a lean concept which refers to all the processes which result in production of the final product or service to the customer. Hence, it includes both value-added and the non-value-added processes.
Q.6 What is Pull in Lean?
Pull refers to the movement in production as per requirements or pull by the customer. Companies produce as per customer need and do not produce as per forecasts.
Q.7 List wastes as in the lean?
Wastes as listed in Lean are: Non-value-added activities, Overproduction, Process and Motion waste, Delays, Transportation, Unnecessary Inventory and defects.
Q.8 List the six sigma level to which the 233 DPMO signify
The five six sigma level has 233 DPMO
Q.9 Why COQ is used in six sigma black belt project?
COQ is used for improving the quality performance.
Q.10 Calculate the takt time for single 8 hour working shift having 1 hour lunch break for customer demand of 480 units per day.
The takt time is 52.5 seconds
Q.11 List the formula for calculating RPN
RPN can be calculated as: multiply Severity Rating, Occurrence Rating and Detection Rating
Q.12 Find the RPN for a process with severity as seven, occurrence of three, and a detection of nine.
The RPN number is 189.
Q.13 Which severity value if 1is least sever and 10 is maximum severe) will you assign if in a automated system which codes the baggage on airport, with its destination does not always record the proper codes?
The severity value to be assigned will be 10 as is essential that the luggage arrives at a proper destination for the customer.
Q.14 Who is a stakeholder in a six sigma black belt project?
A stakeholder in six sigma black belt can be an individual or department or anyone having an interest or is impacted by the six sigma black belt project.
Q.15 How to identify stakeholder for a six sigma black belt project?
We can identify stakeholder for a six sigma black belt project by listing all individual or department or anyone being impacted or having an interest. We can also conduct stakeholder analysis for the purpose as well.
Q.16 How will you manage a difficult stakeholder in the six sigma black belt project?
A six sigma black belt project if implemented will impact various entities in the company. Stakeholder is important part of a six sigma black belt project and a difficult stakeholder may slow or obstruct the project. Addressing issue pertinent to them, listening to them and having clear communication without any bias, helps manage difficult stakeholder.
Q.17 What is SIPOC?
SIPOC is a diagram which shows the suppliers, inputs, processes, outputs, and customers and helps to improve the process and identify any inefficiency.
Q.18 What is the utility of the np chart in six sigma black belt project?
The np chart in six sigma black belt project is used for defectives and to monitor the effects of process improvements. It also assesses the process stability and predictability.
Q.19 What is inter-piece variation in a six sigma black belt project?
It is the variation within a piece, batch, lot, etc, in multi-vari chart.
Q.20 What is your leadership style to manage the six sigma black belt project?
Leadership style depends upon the tasks involved and to be addressed according to which the leadership style can be: Democratic, autocratic or liaises faire.
Q.21 How will you address any conflict appearing within the six sigma black belt project team?
Conflicts within the project team can be managed by using any of the conflict management technique as per situation, the technique can be: collaborating, forcing, accommodating, avoiding or compromising.
Q.22 How will you address under performance by the six sigma black belt project team?
Under performance requires getting to the root of the problem which is present in the process or being faced by the team. It also involves listening to the team members for problem being faced, developing a motivated environment and continuously monitoring for addressing any underperformance event.
Q.23 When to use a c control chart in a six sigma black belt project?
A c control chart is used if we have equal-sized subgroups.
Q.24 What is the condition to use the u control chart in six sigma black belt project?
If subgroup sizes are not constant or not equally sized, then we use the u control chart
Q.25 Describe Bias in a six sigma black belt project
Bias in six sigma black belt project the difference amongst the known values and is a systematic error.
Q.26 What is balanced design in six sigma black belt project?
A balanced design in six sigma black belt project refers to all of the treatment combinations have the same number of observations.
Q.27 What is 5S methodology?
5S methodology is a lean methodology for creation and maintenance of a safe, clean and efficient workplace by eliminating wastes in a project.
Q.28 Describe brainstorming
Brainstorming is a group technique which involves a group of people who contribute ideas for solving a problem.
Q.29 What does the scatter diagrams display in a six sigma black belt project?
The scatter diagrams shows correlation or relationships between two factors.
Q.30 What is the utility of a prioritization matrix in a six sigma black belt project?
A prioritization matrix prioritizes items, tasks or processes based on specific criteria.
Q.31 What is Alpha and Beta risk or what is the P-value?
Prior to explaining alpha and beta risk, you should know what is H0 and Ha, where H0 is acceptable when we have p-value more than 0.05 or 5% and if it is lesser, we accept Ha such that what we accept or reject could be wrong assumptions, that time we are on risk, which could be alpha and beta risk. P-value is the probability, when we are at 95% confidence with our sample, then we are at 5% of risk chances or probability. But if the p-value is more than 5%, that time we go as per H0, as risk is at higher side, however, if the p-value is lesser than 5%, it is suggested to take the risk and accept Ha.
Q.32 Calculate DPU if there are 19 defects in a sample of 200 items.
The DPU is 0.095
Q.33 If the data is non-normal, what hypothesis test should we do?
In case the data is non-normal, we are required to make the data normal, but if we cannot, then we must use the non-normal hypothesis testing, as per their subgroup size. Post the analyse phase, questions can be asked about improvement plans or the tools used. Such that the improvement can be done using the FMEA, therefore we should know about FMEA and 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.
Q.34 Find the PPM if 15 out of 100 customers waited more than 10 minutes for their service
The PPM is 1,50,000.
Q.35 When starting a Six Sigma project, what should be handled first?
At first you are required to check whether that process is in control or not, such that if the data is normal or not, or if the process is not stable, we cannot run the project, we need to make process stable. Also 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.
Q.36 Describe VOC in a six sigma black belt project.
VOC in six sigma black belt project refers to the process of capturing the external customer requirements (like value, price, etc.) and expressed in their language.
Q.37 What are the different Six Sigma levels available?
As we know Six sigma is a process improvement methodology where the focus is on identifying root cause of the errors and thereby helps in improving the overall process. For Six sigma level, we need to check with DPMO score. In case the accuracy of the process gets to a level where it has only 3.4 defects per million opportunities. Such that the list of defects per million which are catered towards a single level are - 690,000 308,537 66,807 6,210 233 3.4
Q.38 What do you understand by balanced scorecard?
A balanced scorecard is a tool to update sponsors or senior management about the progress of a process and groups ongoing measures into four areas, as: finance, process, people, and innovation.
Q.39 What is the primary role of executive leaders or executive management in terms of implementing six sigma team?
Executive Management are the individuals responsible for driving initiatives to ensure their product quality and processes are optimized to a profitable level where the entire team is being productive with fewer operations costs incurred. Usually, the executive leaders will be CEO or Board of director members etc. Such that the primary objective is to make sure that they deliver a quality product to the customers and ensure satisfied users.
Q.40 What is the use of MSA in a Six Sigma Black Belt project?
MSA expands to Measurement System Analysis and is used for verification of the measurement system on parameters like accuracy, etc.
Q.41 Which hypothesis test should be used to ascertain improvement of the workers’ performance before and after training?
Paired sample t-test is a statistical technique that is used to compare two population means in the case of two samples that are correlated. Paired sample t-test is used in 'before-after' studies, or when the samples are the matched pairs, or when it is a case-control study. It is used to compare two population means where you have two samples in which observations in one sample can be paired with observations in the other sample. Hence, as all worker's performance before and after training needs to be studied, hence paired t-test is suitable for the task
Q.42 What is the objective of using the control chart?
The control chart represents the process capability, once special causes have been identified and removed from the process. Day-to-day control charts help identify assignable causes to any variations that occur. Control charts are special types of time series charts in which control limits are calculated around the central location, or mean, of the variable being plotted.
Q.43 What is the theory of constraints?
Theory of constraints is a methodology for identifying the most important limiting factor (i.e. constraint) that stands in the way of achieving a goal and then systematically improving that constraint until it is no longer the limiting factor. Most constraints are the result of policies.
Q.44 What is used in a visual factory ?
Visual factory is a combination of signs, charts and other visual representations of information that enable the quick dissemination of data within a lean manufacturing process. The visual factory attempts to reduce the time and resources required to communicate the same information verbally or in written form, as both are viewed as a "waste" within the framework of a lean manufacturing process.
Q.45 Which technique reduces changeover times?
SMED or Single Minute Exchange of Dies is the technique for reducing changeover time to change a process from running a specific product manufacture to another. It enables flexibility in final product offerings and also to address smaller batch sizes.
Q.46 What is formula for DPMO?
Defects per million opportunities (DPMO) is the average number of defects per unit observed during an average production run divided by the number of opportunities to make a defect on the product under study during that run normalized to one million. It is calculated as DPO×1,000,000
Q.47 What is the standard deviation for a process giving nonconformities as per Poisson distribution with the mean of the nonconformities is 25?
Poisson is used for situations when an attribute possibility is that each sample can have multiple defects or failures. The standard deviation is a measure of the spread of scores within a set of data. The standard deviation formula is very simple: it is the square root of the variance. The Poisson distribution applies when: (1) the event is something that can be counted in whole numbers; (2) occurrences are independent, so that one occurrence neither diminishes nor increases the chance of another; (3) the average frequency of occurrence for the time period in question is known; (4) it is possible to count how many events have occurred, such as the number of times a firefly lights up in my garden in a given 5 seconds, some evening, but meaningless to ask how many such events have not occurred. Hence, after computing the standard deviation for Poisson distribution, it results in 25.
Q.48 What should user infer, if the number of distinct categories for a measurement system using a micrometer is 1?
The number of distinct categories signify the usefulness of a measurement system for a product. It gives the number of divisons that the measurement system can accurately measure across process variation. If the index is less than 2, it is useless for study as, the minimum acceptable value is 5. As micrometer is being used in the question or in decimal places but, a value of 1 is below the minimum.
Q.49 Which tools is commonly used in the define phase of a project?
The word affinity means a ‘‘natural attraction’’ or kinship. The affinity diagram organizes ideas into meaningful categories by recognizing their underlying similarity. It reduces data by organizing large inputs into a smaller number of major dimensions, constructs or categories. It organizes facts, opinions and issues into natural groups to help diagnose a complex situation or find themes. It is used in define phase to organize a lot of ideas and identify central themes in them.
Q.50 Which factor is responsible for implementing six sigma?
Profit improvement is the primary reason for companies to engage and undertake quality improvements by six sigma. Six sigma is not just quality improvements but also providing better value to customers, investors and employees. Six Sigma is a business initiative or a way of doing business which improves quality and productivity, increases competitiveness and reduces cost. By controlling the amount of variation within the allowable upper and lower limits of a process, the frequency of out of control conditions reduces. Making six sigma as part of doing business reduces errors, identifies and corrects deviations in processes and impacts the success of the organization.
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