Certified Six Sigma Black Belt Measurement System Analysis Questions and Answers

Question 1

A Gage R&R study was performed to evaluate a measurement system. The results show that the %Contribution for the total Gage R&R is 25%, with repeatability accounting for 20% and reproducibility for 5%. The part-to-part variation is 75%. What is the most appropriate conclusion and next step?

Accepted Answer

The measurement system is unacceptable because the total Gage R&R variation is too high, and the primary issue is with the measurement device itself.

Answer

According to AIAG (Automotive Industry Action Group) guidelines, a %Contribution for Gage R&R greater than 9% is considered unacceptable. In this scenario, the 25% total is well above this threshold. Repeatability, or Equipment Variation (EV), represents the variation when the same operator measures the same part multiple times and is associated with the gage itself. Reproducibility, or Appraiser Variation (AV), is the variation when different operators measure the same part. Since repeatability (20%) is the dominant source of measurement error compared to reproducibility (5%), the primary problem lies with the measurement instrument (the gage), not the operators.

Question 2

A Black Belt is conducting a Measurement System Analysis on a new digital scale. They measure a certified 10.00kg standard weight multiple times across the scale's operating range (from 1kg to 50kg). They find that the average measurement for the 10.00kg weight is 10.05kg, but for a 40.00kg standard weight, the average measurement is 40.30kg. This issue, where the magnitude of the error changes across the measurement range, is known as a problem with:

Accepted Answer

Linearity

Answer

Linearity is defined as the change in bias over the operating range of the measurement instrument. The scenario describes a situation where the systematic error (bias) is not constant; it increases as the weight being measured increases. This indicates a linearity problem. Stability relates to how the measurement system performs over time, while repeatability and reproducibility relate to the precision (consistency) of the measurements, not the systematic accuracy across the range.

Question 3

An Attribute Agreement Analysis is being conducted for a visual inspection process where operators classify products as 'Pass' or 'Fail'. Which of the following is the primary goal of this type of study?

Accepted Answer

To assess the consistency of the appraisers' judgments against a standard and against each other.

Answer

Attribute Agreement Analysis is specifically designed for discrete or attribute data (e.g., pass/fail, go/no-go). Its purpose is to evaluate the quality of an attribute measurement system by assessing how well appraisers agree with themselves (repeatability), with each other (reproducibility), and with a known standard or expert appraisal (accuracy). Bias and linearity are concepts associated with continuous (variable) measurement systems. Process capability and control charts are process analysis tools, not tools for evaluating the measurement system itself.

Question 4

In the context of a Gage R&R study, which of the following best describes 'reproducibility'?

Accepted Answer

The variation observed when different appraisers measure the same part multiple times using the same gage.

Answer

Reproducibility, also known as Appraiser Variation (AV), is the variation in the average of the measurements made by different appraisers when measuring the same part. It quantifies the consistency between different people. In contrast, repeatability is the variation from the gage itself when used by a single appraiser, bias is the difference from the true value (accuracy), and stability is the consistency over time.

Question 5

A Six Sigma team analyzes the output of a Gage R&R study and finds that the Number of Distinct Categories (ndc) is 2. What does this value indicate about the measurement system?

Accepted Answer

The measurement system is only able to divide the process data into two groups, which is inadequate for process control.

Answer

The Number of Distinct Categories (ndc) is a metric that indicates the resolution of the measurement system relative to the process variation. An ndc of 2 means the gage can only distinguish between two groups of parts (e.g., 'high' and 'low'). An ndc of less than 5 is generally considered unacceptable for process analysis and control, as the measurement system cannot adequately distinguish between parts within the process spread. An ndc of 5 or more is typically desired.

Certified Six Sigma Black Belt Exam Practice Test

Certified Six Sigma Black Belt Exam Practice Test

Certified Six Sigma Black Belt Measurement System Analysis Questions and Answers