Six Sigma Interview Questions and Answers

Sig-Sigma is an essential methodology for any business process to bring significant improvement by identifying flaws and weaknesses. Over the years, Six Sigma practitioners have developed tools and methods to reduce defects and waste through control and problem-solving. The widely used Six Sigma tools are: 

• DMAIC: This tool includes five steps, Define, Measure, Analyze, Improve, and Control. A DMAIC process allows continuous improvement in manufacturing methods through data and measurable goals. 
• The five Whys: This method is deployed at the Analyze phase in DMAIC. The five whys work like that, 

1. Write down problems to make the team focus on them 
2. Ask why the issues happen 
3. If not, get the answer, and ask again why? 
4. Repeat the why at least five times to get the correct source of the issue 

• 5S system: The 5S System organizes workplace materials to facilitate easier access and better management. This system eliminates waste that is generated by poor working conditions and workstations that are inadequate. The 5S stands for: 

1. Sort only necessary items 
2. Set all items and label them 
3. Shine your work area by cleaning 
4. Standardize your set standard and sort them 
5. Sustain by executing all the standards by practicing regularly 

• Value Stream Mapping: This tool helps to improve and optimize the flow of materials and information in the organization. It identifies three things,

1. Identify the activities when they are enabled; they add value 
2. Identify the value-added activities 
3. Identify non-value added activities and eliminate them 

• Regression Analysis: It is a statistical tool used to estimate and understand the relationship between two variables by defining a mathematical relationship between input and output variables. Graphing these inputs and outputs helps you visualize patterns or deviations from desired patterns in your workflow.
• Pareto Chart: This is an essential tool of Six Sigma since it helps identify 20% of resources that result in 80% of process mistakes. It gives you a clear indication of which components need your immediate attention. 

Six Sigma aims to deliver quality products to the customer. As well as reducing output variation, it seeks to predict process results. Measuring, analyzing, improving, and controlling are the steps in this process. Variation refers to the amount by which the output deviates from the actual output. The variations used in Six-Sigma are; 

Mean: Mathematical averaging techniques are used to measure and compare the variations. Then, a specific application is measured, and a mean is calculated. 

Median: In this, variations are measured and compared using the midpoint. It is calculated by finding the highest and lowest values and dividing them by two.

Range: It differentiates between high and low values in a given data range. 

Mode: Most occurred values in the given data. 

The Six Sigma team members belong to different departments; however, all work with the same goal to produce a quality service. The Six-Sigma team consists of: 

• Six Sigma Deployment Leader: They set the business objectives and create a successful environment.
• Six Sigma Champion: Project Champions or sponsors are business, function, or value stream managers whose businesses, operations, or value streams are considered high priorities. They ensure process improvements are captured and sustained since they own the business's processes. 
• Six Sigma Master Black Belt: These individuals develop sig-Sigma strategies and supporting tactics based on high-level business goals. The team coordinates and leads cross-divisional value streams like customer service, Research, etc. Moreover, they promote a culture of openness, creativity, and challenge. 
• Six Sigma Black Belt: These are full-time or part-time leaders who guide green belts and other associates through the implementation of projects. They are responsible for technical responsibility to execute specific tasks and ensure that all the changes are implemented and sustained. 
• Six Sigma Green Belt: These are the engine of the projects; the goal of green belts is project execution, team and project structuring, and sharing of best practices. 
• Six Sigma Yellow Belt: After the project has been completed, this team also plays a crucial role in transferring the process improvements from Six Sigma to other parts of the organization.

This is one of the most frequently asked lean six sigma interview questions and answers for freshers in recent times.

DMAIC and DMADV are the two frequently used Six Sigma methods that increase the effectiveness and efficiency of the business process. While the two approaches have some fundamental similarities, they are not interchangeable because they were designed for use in different business processes.

DMAIC stands for Define, Measure, Analyse, Improve, and Control and is used to improve the existing process. It is a reactive and process-focused method that needs a small team continuously working for improvement. It is a corrective approach using statistical and quantitative tools to implement incremental changes. 

DMADV stands for Define, Measure, Analyze, Design, Verify and is used to seek new processes. It is a proactive, customer-focused method that needs a large team to reengineer the services. It is a preventive approach using qualitative tools to implement evolutionary changes. 

The fishbone or Ishikawa concept is a visualization tool to understand the relationship between "cause and effect" to solve an issue. The tool is beneficial since it illustrates the root of a problem or a phenomenon, what factors play a crucial role in causing those problems or phenomena, and how to resolve the situation. An Ishikawa is drawn in the shape of a fishbone, allowing you to understand what drives and affects the relationship you are trying to understand.

When to use the Fishbone diagram? 

• When there are multiple problem causes 
• Identifying the root causes 
• Sort the interaction between factors and effects 
• Initiate corrective action for problems 

Steps to draw a fishbone diagram 

1. Identify and write the problems that need to be analyzed clearly 
2. Draw a horizontal line called spine; at the right end of the spine, draw a box and write the determined problem in a box. 
3. Identify major causes and write them down above and below the horizontal line. These causes are men, methods, machines, materials, measurements, and the environment. 
4. Brainstorm and link the sub-causes to the leading causes 
5. Finally, the fishbone diagram is ready for analysis. Analyze all the possible causes of an effect and use the 5why analysis to identify possible causes. 

The purpose of load testing is to determine a system's Performance under real-life load conditions. This type of testing aims to explain how an application responds when multiple users access it at the same time. Load testing identifies the following conditions; 

• Verify the maximum capacity of an application 
• Verify whether the infrastructure is suitable for running an application 
• Verify the application's sustainability 
• Their concurrent users, scalability categorizes applications, and the number of simultaneous users they can support. 

There are different types of load testing, 

1. Load testing examines the application's reaction time and tests the workload built under typical circumstances. 
2. Stress testing determines the load point at which your application will crash by applying a hefty workload. 
3. Spike Testing  This involves exchanging workload instantly and monitoring application response in real time. 
4. Durability testing exposes the application to the anticipated workload for a long time to see how well it can manage it. 
5. Reliability testing In this test, the workload will gradually increase to see how well the program can handle more work. 
6. Volume testing Aims to test the software's database's data processing capacity and cost-effectiveness by feeding it large volumes of data. 

An approach to Six Sigma involves converting a practical problem into a statistical problem, solving it statistically, and then converting the statistical solution back into a functional problem. There are widely used statistical tools; 

• Gage R&R: You may check the reproducibility and repeatability of continuous measures like pressure, weight, and diameter with the Gage R&R. It assists in determining whether the measurements are accurate. 
• Histogram: The term histogram refers to a snapshot of continuous, numerical data. It helps you identify the spread and center of data much faster. This tool lets you locate maximum data and provides information about maximum and minimum values. 
• ANOVA: One of the frequently utilized Six Sigma techniques businesses employ worldwide is ANOVA, a group of statistical models applied to study mean differences. Simply put, this statistical tool makes comparing two or more means straightforward. 
• Regression: Six Sigma regression is a statistical tool used to determine whether an input and output variable are related. An example of how you can use the device is to determine whether a company's sales revenue and marketing expenditure are related. 
• T-test: Another statistical technique for comparing the average of one sample to the average of another sample is the t-test. The average of one sample can also be compared to a predetermined target using this method. 
• DOE: To ascertain any links between the inputs and outputs, Design of Experiments (DOE) provides a data gathering technique to change the information. This tool can find the best settings after gathering essential data and identifying crucial inputs. 

The standard deviation is the square root of variance measured as a measure of dispersion in a dataset. A standard deviation is calculated by determining each data point's deviation from the mean and taking the square root of that. Standard deviation is often referred to as SD and is indicated by the symbol "σ."

Steps to calculate SD: 

• Calculate the arithmetic mean
• Calculate the squared differences from the mean by (The data value-mean)2 
• Calculate the squared differences' average (Variance = sum of squared differences / the number of observations) 
• Calculate the square root of the variance (Standard deviation = √Variance) 

Expect to come across this, one of the most important lean six sigma interview questions for experienced professionals in quality management, in your next interviews.

Six Sigma's analysis phase is one of its most essential components. The analysis aims to identify defects, errors, and waste within a project and map out exactly what happened. An effective tool for discovering associations between variables in data, regression analysis cannot necessarily show causality. As a result, it has several applications in business, finance, and economics. It is used, for instance, to assist investment managers in valuing assets and comprehending the connections between variables like commodity prices and the stocks of companies that trade in those commodities. 

Regression analysis is most often connected with the analysis stage of the DMAIC (define, measure, analyze, improve, and Control) five-step Six Sigma methodology. DMAIC enables businesses to streamline current procedures and get rid of errors. Regression analysis is one of the various tools used in the Six Sigma analysis phase. 

Lean can also employ regression analysis to identify wasteful regions. It enables both the use of data to make predictions and the measurement of whether outcomes are consistent with expectations when a process variable is altered. 

Defect, any product or service that deviates from the specifications is said to have a defect. A defect does not automatically preclude the use of a good or service, and a defect only signifies that the end product did not turn out strictly as intended. 

Defective, A product or service that is entirely unusable is deemed to be faulty. There are only two options: either each product or service is deemed defective or not.

An item with a fault has one or more defects. Nevertheless, not all damaged things are defective, depending on the flaw's seriousness. 

FMEA stands for Failure Modes and Effects Analysis. FMEA is a proactive strategy for assessing a process to determine where and how it might fail and to gauge the relative impact of various failures to pinpoint the areas of the process that require the most significant improvement. FMEA is used when,

• Improve an existing process. 
• Establishing a new process before putting it into use in a production environment. 
• Looking for quality control (QC) problems that occur within a process. 

The following are types of FMEA 

1. DFMEA (Design Failure Modes and Effects Analysis) 

A DFMEA is concerned with a good or service, and these are often carried out before creating new goods or services or whenever a change is made to their designs. When you do one, you consider potential errors, safety risks, and legal and regulatory difficulties with the finished product. 

2. PFMEA (Process Failure Modes and Effects Analysis) 

A PFMEA examines a procedure. In contrast to a DFMEA, it simply analyzes the final good or service to identify problems with a production process. You'll more frequently take a look at the process's results. Why do these two items vary from one another? Because most goods and services result from several processes rather than a single one. 

3. SFMEA (System Failure Modes and Effects Analysis) 

A system failure mechanisms and consequences study broadly views the entire system. One involves looking at things like how processes and components are related. Problems might arise outside of methods or with particular machines; therefore, an SFMEA can be helpful. They also happen when several machines or processes work together. 

X-Bar and R charts are Six Sigma's most potent quality control tool to monitor the process. They visualize variations, identify problems, predict the range of outcomes, and analyze patterns of process variation. These tools are commonly used in lean six sigma projects during the control phase.  

X-bar chart: It is the average deviation from subgroup values in a process over time. The control limits on the X-Bar account for the sample's mean and center. 

R-Charts: This keeps track of how quickly the process is spreading.  

Quality control charts like the x-bar and R-chart are employed to keep track of a process's mean and variation using samples gathered over a predetermined period. 

Brainstorming is a valuable Six Sigma tool used for problem-solving, evaluating pieces of information, stimulating creativity and developing ideas, and participating in the impromptu discussion. In Six Sigma, brainstorming is used in many ways,

• It helps to find the root cause of the problems by incorporating with fishbone diagram and 5Whys methods.
• It helps in creating SIPOC.
• It helps in creating a process map.

Tools to keep Brainstorming structured:

• Affinity Diagram: In affinity diagramming, large amounts of language data are organized according to their natural relationships to create groupings. The affinity diagram can be used to gather many ideas from a group of participants before others' ideas influence them.
• Fishbone Diagram: The fishbone diagram is one of the simplest yet most effective tools in brainstorming sessions for categorizing the sources of an issue to determine its root causes.
• Brainstorming Maps: The best way to visualize brainstorming ideas is to use a diagram with a central root and branches radiating. It is a visual thinking tool that aids information structuring, enhancing your capacity for analysis, comprehension, synthesizing, memory, and idea generation.

1. This graphical representation of a process allows you to analyze boundaries and edges, understanding where the product goes. The diagram contains geometric symbols that depict the materials, services, and resources involved in the methods and the directions needed to achieve the result (product or service). 
2. Since the flow chart has the primary mapping function, this tool is essential because it is necessary to measure a process to improve it. 

Symbols used in Flowcharts:

Types of Flowcharts: 

1. Block Diagram: The most straightforward flowchart ever created. It acts as a process sequencing because it consists of blocks and does not include any decision points. It is employed as direct work instructions (ITs) or when a more comprehensive depiction of a process is desired. 
2. Process Flowchart: While it resembles a block diagram, it also has decision points. 
3. Functional Flowchart: This flowchart shows how a process is carried out between sections or areas. This type of flowchart is widely used for functions that don't restrict themselves to a single area. Since the responsible party is identified for each phase, any bottlenecks can be identified. 
4. Vertical Flowchart: Process Diagrams, also called vertical flowcharts, consist of symbols and patterns in vertical columns. It is used in studies of productive processes because it provides speed of filling, clarity of interpretation, and ease of reading.

A must-know for anyone looking for top six sigma interview questions, this is one of the frequently asked six sigma behavioral interview questions.

The lean SIX Sigma methodology aims to reduce problems, eliminate waste, and improve working conditions to improve customer service. It combines lean six Sigma's tools, methods, and principles to enhance your organization's operations. Globally, businesses have seen dramatic improvements in profitability due to lean six Sigma's team-oriented approach. 

The difference between Lean Six Sigma and Six Sigma are: 

1. Lean Six Sigma is waste-focused, whereas Six Sigma works on variation and any deviation from the target.
2. Lean Six Sigma uses visual techniques, while Six Sigma uses statistical tools to analyze and solution creation. 
3. The Lean solution is documented using a redesigned value stream map, frequently resulting in changes to work instructions and workflows at numerous process phases. In addition, changes in setup procedures and the control plan for observing the process and reacting to variation are included in the documentation of the Six Sigma solution. 

Lean Six Sigma, which enables businesses to use data to reduce process flaws, has emerged as one of the most powerful frameworks for delivering better goods and services while still being effective. The benefits of using Lean Six Sigma are: 

1.  Improve customer satisfaction: Customer satisfaction is one of the crucial metrics to measure the success of any organization. And lean Six Sigma reduces the ratio of dissatisfied customers by identifying the root cause and continues to work towards making products customer satisfaction.
2.  Increase Productivity: The Six Sigma methodology allows organizations to measure time spent on work activities and identify the root causes of productivity issues. Rather than beating around the bushes blindfolded, Six Sigma will assist you by collecting business-critical data from different locations.
3. Reduce project lifecycle: In most cases, enterprises run over the original deadline for a project due to changes in project scope or management policies. An organization implementing the Six Sigma methodology can form an exclusive team that includes professionals from all levels and departments. The team is then responsible for identifying critical factors that can negatively affect the project, causing it to run over its schedule. Once the project manager has discovered the root cause of the problems, they can be assigned to find solutions. As a result, project lifecycle times can be shortened by 35%.
4. Reduce the cost: Problems are reduced by the Six Sigma process to 3.4 defects per million opportunities. An organization will ultimately lower the cost of achieving quality by 20% and boost operational revenue by 50% if it spends less time mending defective items.
5. Time Management: Employers using the Lean Six Sigma technique can assist their staff with time management, leading to more productive staff members and an effective firm. The data principles of Six Sigma can be applied to the SMART (specific, measurable, attainable, results-focused, and time-bound) goals that employees are asked to set. This can be used in three main areas: learning, Performance, and fulfillment.

Don't be surprised if this question pops up as one of the top interview questions for six sigma in your next interview.

The techniques and tools used to achieve the goals of lean Six Sigma are based on the type of analysis in which they will be used, and according to this, there are the following tools, 

1. Process Analysis Tools: These tools describe the process and understand its efficiency.

• Process Map is a graphical representation of the link between the process and decision points. 
• The value stream Map includes the steps of the customer value in the process. 
• Data boxes record the cycle time, resources, value-added time, etc. 
• TAKT time reflects the time allotted to each process. 
• Value-added time is the amount of processing time spent on a single item moving through the process when adding a component of customer value takes place. 
• Kanban visual task scheduling tool. 
• Visual Control signals the process bottlenecks and helps to relieve those. 

2. Visual Analysis Tools: Virtually all problem-solving methodologies use visual analysis tools and techniques. These methods can be applied at various stages, and they are valuable since they are rapid and straightforward to comprehend. They are also great ways to communicate with senior management and the operations or organizations that the solution will affect.

• Histogram 
• Fishbone 
• Pareto chart 
• Scatter diagram 
• Run chart 
• Pie chart 
• Box Plots 
• Check sheets 

3. Project and Team management: Customers and stakeholders must be able to communicate with lean six sigma projects. Numerous methods have succeeded in this area. Organizing and communicating with internal stakeholders, such as team members, might benefit from some of these strategies, some of which are founded on comprehending the viewpoint of external stakeholders. 

• CTQ, i.e., critical to quality, is used to measure the product and the process by the stakeholders. 
• The project charter is a project management document that sets parameters for the activity's scope and authorizes the project. 
• SIPOC  
• Cross-functional team 

The SIPOC acronym stands for, Suppliers, Inputs, Process, Outputs, Customer; all these areas help to create a process map. Each process begins with suppliers offering the process's inputs, which produce the output given to customers. 

Benefit: 

• Define the new process 
• Provide a complete project overview to all stakeholders 
• Initiate problem-solving 
• Keep all the stakeholders on the same page 

How to create SIPOC:  

With the subsequent steps, SIPOC is a table that records the process, output, client, input, and supplier in a table format. 

1. Identify the process for which SIPOC is to be created. 
2. Define the planned steps that typically add value to the inputs to produce consumer outputs. A high-level process flow should only have up to 7 phases; any more makes it difficult to understand. Instead, use an affinity diagram to condense complicated procedures into a handful of essential steps. 
3. List the outputs, like products, services, and information valuable to the customers. 
4. Identify the customers or users of the product. 
5. Determine the inputs, i.e., material and service used by the process to produce. 
6. Identify suppliers 
7. Validate the diagram before moving to the process improvement stage. 

DFSS stands for Design for Six Sigma. The Design for Six Sigma technique aims to increase product and service quality by minimizing variance at the source. The DFSS strategy uses trials and data analysis to design, implement, and improve products and services. Through the development of goods and services that are more useful, effective, efficient, safe, and long-lasting, the aim is to decrease waste across all processes and increase customer satisfaction. 

Benefit:

• DFSS allows improved communication between all stakeholders, including teams and customers. 
• When all designs adhere to the identical procedure and use the same equipment, it is much simpler to create standardization within an organization. 
• By guaranteeing that each project's component serves just one goal, DFSS also contributes to reducing waste. 

ARMI stands for:

Approvers, Sponsor, or business leaders 

Resources, experts whose skills are needed 

Members, team members 

Interested party, team members who need to be informed of project status 

These labels serve as a tool for classifying all the people and their abilities who can contribute to a project's success. ARMI helps the lean six sigma practitioner to identify the stakeholders and create an engagement plan. It also helps to understand different skills and resources early in the project.