16. Measurement Systems

Question 1

Bias P.251

Answer 1

Systematic difference between the mean of the measurement results and a reference or true value. AKA accuracy.

Question 2

Bias: Linearity P. 252

Answer 2

The difference in bias through the expected operating range of measurements. (over operating range)

Question 3

Bias: Stability (of a measurement system) P. 252

Answer 3

Change in bias of a measurement system over time and usage when that system is used to measure a master part or standard. (over time)

Question 4

Precision P.253

Answer 4

The closeness of agreement between randomly selected individual measurement results or test results.

Precision depends only on the distribution of random errors, not reference or true value.

Question 5

Precision: Repeatibility (measurement range) P.254

Answer 5

Independent measurement results are obtained with the same method on identical measurement item with same operator/ equipment within a shot period of time. (Equipment variation or within-system variation)

Question 6

Precision: Reproducibility (measurement average) P.255

Answer 6

Independent measurement results are obtained with the same method on identical measurement item with different operators/ equipment. (Appraiser variation)

Question 7

Discrimination: P.256

Answer 7

Measurement system’s capability to detect and indicate small changes in the characteristic measured.

Question 8

Precision-to-tolerance ratio (PTR) P.256

Answer 8

Measure of the capability of the measurement system. ( Less 0.10= Good, >0.30 require improvement)

PTR= 6σ(ms) / USL - LSL

σ(ms) is the estimated SD of the total measurement system variability.

(ms) measurement system

Question 9

Gage R&R P.257

Answer 9

Measurement system analysis done to evaluate the performance of a test method or measurement system.

Question 10

Percent agreement. P.257

Answer 10

Percentage of time in an attribute GR&R study that appraiser agree with 1. themselves 2.other appraisers, 3, known standard.

Question 11

GR&R measurement adequacy criteria P.257

Answer 11

1. Total percent GR&R in the percent study variation ( Less 10% = Good, 10-30%= Marginal, >30%= inadequate)
2. Percent tolerance ( Less 10% = Good, 10-30%= Marginal, >30%= inadequate)
3. Percent contribution ( Less 1%= Acceptable, 1-9%, Marginal, >9%- inadequate)
4. Number of distinct categories. Min. of 5 level (discrimination)

Question 12

Components of a measurement system P.258

Answer 12

1. Measurement instrument
2. Appraisers (Operators)
3. Methods or procedures for conducting the measurement
4. Environment

Question 13

Type of measurement systems analysis P. 258

Answer 13

• Variables

- Attributes

Question 14

Variable analysis

Answer 14

1. AIAG method
2. ANOVA method
3. Control Chart method

Question 15

GR&R Report (AIAG) P. 262

Answer 15

• Equipment Variation (EV), standard deviation of the variation due to repeatability
• Appraiser variation (AV), standard deviation of the variation due to reproducibility.
• GR&R, estimated of the standard deviation of the variation due to measurement system.
• Part-to-Part variation (PV), standard deviation of the variation due to part differences.
• Total variation (TV), estimated of the standard deviation of the total variation

Question 16

Attribute analysis

Answer 16

1. Attribute agreement analysis

2. Attribute gage study - Analytic Method

Question 17

Attribute agreement analysis P. 269

Answer 17

• Each appraiser versus standard
• Between appraisers
• All appraisers versus standard
• Within the appraiser

Question 18

Attribute gage study - Analytic Method

Answer 18

Used to determine the amount of bias and repeatability of a measurement system when the response is an attribute variable.

Question 19

Causes of measurement error (6M)

Answer 19

1. Machine
2. Methods
3. Man or woman (appraiser)
4. Mother Nature
5. Materials (parts)
6. Measurement
   (7) Management