Lean Six Sigma Green Belt Measure Phase and Statistics Questions and Answers — Questions and Answers
Question 1: A Six Sigma team is analyzing the measurement system for a critical process characteristic. They conduct a study where multiple operators measure the same set of parts multiple times. The goal is to determine how much of the observed variation is due to the measurement equipment versus the people using it. What is this type of study called?
- Process Capability Analysis (Cp/Cpk)
- Failure Mode and Effects Analysis (FMEA)
- Design of Experiments (DOE)
- Gage Repeatability & Reproducibility (R&R) Study (Correct answer)
Correct answer: Gage Repeatability & Reproducibility (R&R) Study
A Gage R&R study is a specific type of Measurement System Analysis (MSA) that assesses two key components of measurement variation: Repeatability (variation from the measurement device) and Reproducibility (variation from different operators). This analysis is crucial in the Measure phase to ensure that the data collected is trustworthy before moving on to the Analyze phase.
Question 2: A project team has collected data on the time it takes to process a customer order. The data includes values like 3.45 days, 2.87 days, and 4.12 days. Which type of data has the team collected?
- Attribute
- Nominal
- Continuous (Correct answer)
- Ordinal
Correct answer: Continuous
Continuous data, also known as variable data, can take on any value within a given range and can be measured on an infinitely divisible scale. Measurements such as time, weight, length, and temperature are classic examples of continuous data. Attribute, nominal, and ordinal data are all types of discrete data, which are based on counts or categories.
Question 3: A process has an Upper Specification Limit (USL) of 65 cm and a Lower Specification Limit (LSL) of 55 cm. A statistical analysis reveals that the process has a Cp of 1.5 and a Cpk of 0.8. What can be concluded about this process?
- The process is both capable and centered.
- The process variation is too wide for the specification limits.
- The process is not centered between the specification limits. (Correct answer)
- The process has a high potential for producing defects due to its spread.
Correct answer: The process is not centered between the specification limits.
Cp measures the potential capability, indicating if the process variation can fit within the specification limits. A Cp of 1.5 suggests the process spread is narrow enough. However, Cpk measures the actual capability by considering how centered the process is. A Cpk less than 1.0 (in this case, 0.8) indicates that the process mean is shifted towards one of the specification limits, making it not centered and likely producing defects.
Question 4: Which of the following is an essential component of a robust Data Collection Plan in the Measure Phase?
- A list of potential solutions to the problem.
- The project's final return on investment (ROI) calculation.
- A detailed schedule for the Improve and Control phases.
- An operational definition of what is being measured. (Correct answer)
Correct answer: An operational definition of what is being measured.
A Data Collection Plan is a structured document created in the Measure phase to ensure data is collected consistently and is relevant to the project. An essential component is the operational definition, which provides a clear, precise description of the metric being measured, how it is measured, and by whom. This removes ambiguity and ensures all data collectors gather information in the same way. The other options are elements of later DMAIC phases or financial justifications.
Question 5: A Green Belt is preparing to collect data to establish a process baseline. To ensure the data is reliable and the measurement system is not introducing excessive variation, what activity should be performed FIRST?
- Calculate the process sigma level.
- Create a control chart for the process.
- Conduct a Measurement System Analysis (MSA). (Correct answer)
- Develop a list of potential root causes.
Correct answer: Conduct a Measurement System Analysis (MSA).
Before extensive data collection for process analysis, it is critical to validate the measurement system. A Measurement System Analysis (MSA) determines if the measurement system's variation is acceptable. If the measurement system is unreliable, the data collected will be flawed, leading to incorrect conclusions in the Analyze phase. Calculating sigma, control charting, and brainstorming root causes all depend on having trustworthy data first.
Question 6: The central tendency of a dataset is being analyzed. The values are: 10, 12, 12, 14, 15, 18, 50. Which measure of central tendency would be MOST affected by the value '50'?
- Median
- Mean (Correct answer)
- Mode
- Range
Correct answer: Mean
The mean is the arithmetic average of all data points, calculated by summing the values and dividing by the count. It is highly sensitive to outliers or extreme values. The value '50' is an outlier in this dataset and will significantly pull the mean upwards. The median (the middle value) and the mode (the most frequent value) are less affected by extreme outliers. While the range is also affected, it is a measure of dispersion, not central tendency.
Lean Six Sigma Green Belt Measure Phase and Statistics Questions and Answers
A Six Sigma team is analyzing the measurement system for a critical process characteristic.
They conduct a study where multiple operators measure the same set of parts multiple times.
The goal is to determine how much of the observed variation is due to the measurement equipment versus the people using it.
What is this type of study called?