10) Data Analysis

Question 1

What is the least squares method?

Answer 1

Best fit line/ line of regression.

Question 2

Explain the difference between accuracy and precision.

Answer 2

Accuracy - how well instrument agrees with true value.

Precision - the dispersion of measurements.

Question 3

Explain the difference between repeatability/ reproducibility.

Answer 3

Repeatability - variation in measurement taken under the same conditions.

Reproducibility - variation in measurements by different conditions, eg different lab measuring same part.

Question 4

How would you test the repeatability/reproducibility of a process?

Answer 4

A Gauge R&R study.

- Determine variability. 
- Determine source of variability.
- Determines the suitability of a measurement 

Precision tolerance ration = k*sqrt(Ym)/ USL-LSL

Question 5

How is a Gauge R&R study carried out?

Answer 5

Parts measured using the calibrated measurement system.

To assess repeatability - same part measured multiple times using same operator.

To assess reproducibility - multiple operators used to do same part.

To assess interactions of operator with part - 5 -10 parts measured.

Question 6

What is gauge R&R short analysis?

Answer 6

• Provides an estimate of variation
• Breakdown of originating errors not possible.

Question 7

What is six sigma?

Answer 7

Define part quality by breaking down in to parts per 100 or parts per thousand.

Typical levels of quality between 2 and 4 sigma.

Question 8

What is the relationship between standard deviation and precision?

Answer 8

The smaller sd is the more precision the instrument has.

Question 9

What are the 2 classes of error sources?

Answer 9

Random and Systematic.

Systematic= remain constant or change in regular fashion.

Random = differences between the results that can not be predicted individually.

Question 10

What are examples sources of error?

Answer 10

• Human error
  
  • Environmental error
    Equipment error