CDG Quality Control & Process Improvement 2

Question 1

When a grading laboratory implements a blind re-grading protocol, what is the primary quality control objective?

Accepted Answer

Eliminate grader bias by preventing access to prior results

Answer

Blind re-grading prevents graders from anchoring to previous results, isolating true consistency and eliminating confirmation bias.

Question 2

A diamond consistently receives VS2 clarity grades internally but is returned from clients graded SI1 by a major lab. Which corrective action addresses the root cause?

Accepted Answer

Conduct calibration sessions using GIA or AGS master comparison stones

Answer

Calibration against industry-recognized master stones aligns internal standards with external benchmarks, addressing the systemic discrepancy.

Question 3

In a Pareto analysis of grading errors, which category of defect should receive priority attention first?

Accepted Answer

The error type representing the largest cumulative percentage of total defects

Answer

Pareto analysis prioritizes the vital few causes that account for the majority (typically 80%) of total defects.

Question 4

Which diamond grading scenario best illustrates a Type I error (false positive) in a quality inspection process?

Accepted Answer

Rejecting a flawless diamond as having an inclusion

Answer

A Type I error (false positive) occurs when a good item is incorrectly rejected — here, flagging a flawless stone as flawed.

Question 5

A grading lab notices that color grades cluster tightly on Monday mornings but spread widely on Friday afternoons. What process variable is most likely responsible?

Accepted Answer

Grader fatigue affecting visual acuity and decision consistency late in the week

Answer

Grader fatigue is a well-documented human factor that degrades the precision and repeatability of visual assessments over long work periods.

(CDG) Certified Diamond Grader Practice Test

(CDG) Certified Diamond Grader Practice Test

CDG Quality Control & Process Improvement 2