Statistical Variation
Analytical testing of paper properties across different facilities often reveals persistent differences in measurement results. This discrepancy, known as inter-laboratory bias, is the systematic difference between the test results obtained by two or more laboratories using the same test method on identical samples. Quantifying this variation is necessary to ensure that quality specifications are met consistently across global supply chains.
Standard test methods must account for this bias to avoid disputes between manufacturers and buyers of packaging board. It represents the offset of a laboratory’s average value from the accepted reference value, arising from differences in instrument calibration or environmental conditions.
Systematic Error
Variation in relative humidity and temperature in testing rooms contributes directly to testing discrepancies. When evaluating tensile strength or bursting resistance, even small shifts in humidity alter the physical performance of the paper. Standardized testing must take place in controlled atmospheres to minimize these variations.
This control is critical for maintaining consistency between supplier and customer measurements.
Calibration Protocol
Regular participation in proficiency testing schemes help laboratories detect and correct systematic deviations. Utilizing certified reference materials allows technicians to adjust their instruments and eliminate the inter-laboratory bias before reporting product data. This alignment ensures that board produced in one region meets the strict standards of a converter in another.
