Flashcards in 16. Measurement Systems Deck (19)
Systematic difference between the mean of the measurement results and a reference or true value. AKA accuracy.
Bias: Linearity P. 252
The difference in bias through the expected operating range of measurements. (over operating range)
Bias: Stability (of a measurement system) P. 252
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)
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.
Precision: Repeatibility (measurement range) P.254
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)
Precision: Reproducibility (measurement average) P.255
Independent measurement results are obtained with the same method on identical measurement item with different operators/ equipment. (Appraiser variation)
Measurement system's capability to detect and indicate small changes in the characteristic measured.
Precision-to-tolerance ratio (PTR) P.256
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
Gage R&R P.257
Measurement system analysis done to evaluate the performance of a test method or measurement system.
Percent agreement. P.257
Percentage of time in an attribute GR&R study that appraiser agree with 1. themselves 2.other appraisers, 3, known standard.
GR&R measurement adequacy criteria P.257
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)
Components of a measurement system P.258
1. Measurement instrument
2. Appraisers (Operators)
3. Methods or procedures for conducting the measurement
Type of measurement systems analysis P. 258
1. AIAG method
2. ANOVA method
3. Control Chart method
GR&R Report (AIAG) P. 262
- 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
1. Attribute agreement analysis
2. Attribute gage study - Analytic Method
Attribute agreement analysis P. 269
-Each appraiser versus standard
-All appraisers versus standard
-Within the appraiser
Attribute gage study - Analytic Method
Used to determine the amount of bias and repeatability of a measurement system when the response is an attribute variable.