Blind Sample is a quality control sample whose true value is unknown to the analyst or operator performing the measurement — the sample is submitted without identification or expected results, eliminating any conscious or unconscious bias in the measurement or data interpretation.

Blind Sample Protocol

• Preparation: A quality manager or independent party prepares the blind sample — the analyst doesn't know it's a QC sample.
• Submission: The blind sample is submitted as a routine sample — measured using standard procedures.
• Evaluation: After measurement, the result is compared to the known value — assesses the measurement system under real conditions.
• Double Blind: Neither the analyst NOR supervisor knows which samples are blind — maximum objectivity.

Why It Matters

• Bias Prevention: Operators may unconsciously adjust measurements when they know the expected result — blind samples reveal true performance.
• Realism: Blind samples test the entire measurement process — sample handling, measurement, and data reporting.
• Regulatory: Some quality systems require blind sample testing — FDA GMP, ISO 17025, clinical laboratories.

Blind Sample is the honest test — measuring a sample without knowing the expected answer to evaluate true measurement performance without bias.