CCIL Laboratory Equipment Calibration 4 — Questions and Answers
Question 1: Which statistical parameter is used to describe the spread of repeated calibration measurements around the mean?
- Mean absolute deviation
- Standard deviation (Correct answer)
- Median
- Range only
Correct answer: Standard deviation
Standard deviation quantifies the dispersion of repeated measurements and is a key component in calculating measurement uncertainty.
Question 2: ISO/IEC 17025 requires that calibration laboratories demonstrate competence through:
- Annual government inspection only
- Proficiency testing and interlaboratory comparisons (Correct answer)
- Manufacturer service contracts
- Customer satisfaction surveys alone
Correct answer: Proficiency testing and interlaboratory comparisons
ISO/IEC 17025 mandates participation in proficiency testing programs to objectively demonstrate measurement competence.
Question 3: What is 'dead weight' testing used to calibrate in laboratory settings?
- Mass balances
- Pressure gauges and transducers (Correct answer)
- Spectrophotometers
- pH electrodes
Correct answer: Pressure gauges and transducers
Dead weight testers use known masses on a piston-cylinder system to generate precise pressure values for calibrating pressure measurement instruments.
Question 4: Which calibration interval strategy adjusts frequency based on actual instrument performance history?
- Fixed calendar-based intervals
- Risk-based adaptive calibration intervals (Correct answer)
- Manufacturer-default intervals only
- Regulatory-mandated static intervals
Correct answer: Risk-based adaptive calibration intervals
Adaptive calibration intervals use historical as-found data to extend intervals for stable instruments and shorten them for drifting ones.
Question 5: When expressing calibration results, the expanded uncertainty is typically reported at a confidence level of:
- 68%
- 90%
- 95% (Correct answer)
- 99.9%
Correct answer: 95%
By convention (GUM), expanded uncertainty U = k × uc is reported at approximately 95% confidence, typically using a coverage factor k = 2.
Question 6: A pipette calibrated to deliver 1.000 mL consistently delivers 0.985 mL. This represents a percent error of:
- 0.5%
- 1.5% (Correct answer)
- 2.0%
- 0.15%
Correct answer: 1.5%
Percent error = |measured − true| / true × 100 = |0.985 − 1.000| / 1.000 × 100 = 1.5%.
Question 7: Environmental conditions such as temperature and humidity must be monitored and recorded during calibration because:
- They are required only for ISO 9001 audits
- They influence measurement results and form part of the uncertainty budget (Correct answer)
- They determine the color of calibration labels
- They affect only chemical test results, not physical measurements
Correct answer: They influence measurement results and form part of the uncertainty budget
Temperature, humidity, and atmospheric pressure affect instrument performance and are significant uncertainty contributors that must be documented.
CCIL Laboratory Equipment Calibration 4
Which statistical parameter is used to describe the spread of repeated calibration measurements around the mean?