CLC Quality Control & Process Improvement 2 — Questions and Answers
Question 1: A laboratory notices its Levey-Jennings chart shows 8 consecutive QC results on the same side of the mean. Which Westgard rule is violated?
- 1-2s rule
- R-4s rule
- 10x rule (Correct answer)
- 2-2s rule
Correct answer: 10x rule
The 10x rule is violated when 10 consecutive QC values fall on the same side of the mean, indicating systematic bias; 8 in a row triggers the warning version of this rule.
Question 2: Which statistical tool is BEST suited for identifying the root cause of a process defect in a laboratory quality improvement project?
- Pareto chart
- Fishbone (Ishikawa) diagram (Correct answer)
- Control chart
- Run chart
Correct answer: Fishbone (Ishikawa) diagram
A fishbone diagram systematically explores all potential causes (equipment, methods, materials, personnel, environment) contributing to a defect.
Question 3: In Six Sigma methodology, a process operating at 4-sigma has approximately what defect rate per million opportunities (DPMO)?
- 3.4 DPMO
- 6,210 DPMO (Correct answer)
- 66,807 DPMO
- 233,000 DPMO
Correct answer: 6,210 DPMO
A 4-sigma process produces approximately 6,210 defects per million opportunities, compared to 3.4 DPMO at the Six Sigma benchmark.
Question 4: A laboratory's reagent blank consistently reads higher than expected. Which type of error is MOST likely present?
- Random error
- Proportional systematic error
- Constant systematic error (Correct answer)
- Gross error
Correct answer: Constant systematic error
A consistently elevated reagent blank indicates constant systematic error (additive bias) affecting all results by the same absolute amount.
Question 5: Which PDCA cycle step involves analyzing data collected during a process change to determine if the improvement was successful?
- Plan
- Do
- Check (Correct answer)
- Act
Correct answer: Check
The 'Check' (or Study) step of PDCA involves evaluating the collected data to assess whether the planned changes achieved the desired improvement.
Question 6: A laboratory wants to reduce turnaround time for stat tests. Using Lean principles, which waste type does unnecessary transport of specimens represent?
- Overproduction
- Motion
- Transportation (Correct answer)
- Waiting
Correct answer: Transportation
In Lean methodology, unnecessary movement of materials (including specimens) between locations is classified as the Transportation waste type.
Question 7: When performing a method comparison study, which statistical measure indicates the degree of agreement between two quantitative methods?
- Coefficient of variation
- Bias and slope from Deming regression (Correct answer)
- Standard deviation of the mean
- Receiver operating characteristic (ROC) area
Correct answer: Bias and slope from Deming regression
Deming regression accounts for error in both methods and provides slope (proportional error) and bias (constant error) to quantify method agreement.
CLC Quality Control & Process Improvement 2
A laboratory notices its Levey-Jennings chart shows 8 consecutive QC results on the same side of the mean.
Which Westgard rule is violated?