Free Lean Six Sigma Green Belt DMAIC: Analyze Phase Techniques Questions and Answers — Questions and Answers
Question 1: A project team in a manufacturing plant is analyzing data to understand the relationship between oven temperature (an input variable, or 'x') and the resulting product hardness (an output variable, or 'y'). Both variables are continuous. Which statistical tool is MOST appropriate for quantifying the strength and nature of this relationship?
- ANOVA
- Regression Analysis (Correct answer)
- Chi-Square Test
- Control Chart
Correct answer: Regression Analysis
Regression Analysis is used to model the relationship between a dependent (output) variable and one or more independent (input) variables. Since the team wants to understand how temperature ('x') affects hardness ('y'), regression is the ideal tool to create a predictive equation and quantify the relationship.
Question 2: What is the primary purpose of conducting a hypothesis test during the Analyze phase of a DMAIC project?
- To brainstorm all possible causes of a problem.
- To visually display the frequency of defects.
- To statistically validate whether a suspected root cause has a significant effect on the process output. (Correct answer)
- To monitor the process performance over time.
Correct answer: To statistically validate whether a suspected root cause has a significant effect on the process output.
Hypothesis testing is a statistical method used to make decisions based on data. In the Analyze phase, it is used to test theories about root causes. For example, a team might hypothesize that 'Shift A' has a different average cycle time than 'Shift B'. A hypothesis test (like a t-test) would determine if the observed difference is statistically significant or just due to random chance.
Question 3: A team is struggling with a high rate of shipping errors. They have gathered experts from the warehouse, sales, and data entry departments for a brainstorming session to identify all potential causes for the errors. Which of the following tools would be most effective for structuring this brainstorming session and categorizing the potential causes?
- Scatter Plot
- 5 Whys
- Pareto Chart
- Fishbone (Ishikawa) Diagram (Correct answer)
Correct answer: Fishbone (Ishikawa) Diagram
A Fishbone (or Ishikawa) Diagram is a visual tool used to categorize and display the potential causes of a specific effect or problem. It is ideal for brainstorming sessions as it helps organize thoughts into logical categories (like Manpower, Method, Machine, Material, etc.), ensuring a comprehensive exploration of potential root causes.
Question 4: After brainstorming numerous potential causes for late deliveries, a project team has collected data on the frequency of each cause. They now need to prioritize their efforts by focusing on the causes that contribute most to the problem. Which tool should they use?
- Pareto Chart (Correct answer)
- Process Map
- Histogram
- Run Chart
Correct answer: Pareto Chart
A Pareto Chart is a bar chart that displays the frequency or impact of causes in descending order, combined with a line graph showing the cumulative percentage. It is based on the Pareto Principle (80/20 rule) and is specifically designed to help teams identify and prioritize the 'vital few' causes that are responsible for the majority of the problems.
Question 5: Which of the following BEST describes the primary function of the 5 Whys technique in the Analyze phase?
- To determine the statistical significance between two variables.
- To graphically display the main categories of potential causes.
- To systematically drill down past symptoms to identify the fundamental root cause of a problem. (Correct answer)
- To compare the means of two or more groups.
Correct answer: To systematically drill down past symptoms to identify the fundamental root cause of a problem.
The 5 Whys is an iterative interrogative technique used to explore the cause-and-effect relationships underlying a particular problem. By repeatedly asking 'Why?', the team can move beyond the immediate symptoms and uncover a deeper, more fundamental root cause that, when addressed, can prevent the problem from recurring.
Question 6: A call center manager wants to determine if there is a statistically significant difference in the average call handling time between a team that received new training and a team that did not. Both teams have fewer than 30 members. What is the most appropriate statistical test to use?
- Chi-Square Test
- 1-Sample t-Test
- 2-Sample t-Test (Correct answer)
- ANOVA
Correct answer: 2-Sample t-Test
A 2-Sample t-Test is used to compare the means of two independent groups to determine if they are statistically different from each other. Since the manager is comparing the average call times (continuous data) of two different teams (two groups), the 2-Sample t-Test is the correct tool.
Free Lean Six Sigma Green Belt DMAIC: Analyze Phase Techniques Questions and Answers
A project team in a manufacturing plant is analyzing data to understand the relationship between oven temperature (an input variable, or 'x') and the resulting product hardness (an output variable, or 'y').
Both variables are continuous.
Which statistical tool is MOST appropriate for quantifying the strength and nature of this relationship?