What bias and precision are acceptable for a validated BP device?

• A. Bias within ±5 mmHg with a standard deviation ≤ 8 mmHg for SBP and DBP
• B. Bias within ±10 mmHg with a standard deviation ≤ 12 mmHg for SBP and DBP
• C. Bias within ±2 mmHg with a standard deviation ≤ 6 mmHg for SBP and DBP
• D. Bias within ±7 mmHg with a standard deviation ≤ 9 mmHg for SBP and DBP

Answer: (A)

The main idea is understanding what makes a BP device reliable: bias tells you how far the readings are, on average, from the true value (systematic error), and precision (often shown by the standard deviation of differences) shows how much those readings vary from one measurement to another.

Validated devices are expected to stay within specific limits for both bias and dispersion. The standard criterion used in many BP device validations is that the average difference (bias) must be within ±5 mmHg, and the variability of those differences (the standard deviation) must be no greater than 8 mmHg for both systolic and diastolic pressures. When a device meets these thresholds, it demonstrates both accuracy (not drifting far from the true value) and reliability (readings don’t scatter too widely).

So, the choice that lists bias within ±5 mmHg with a standard deviation ≤ 8 mmHg for SBP and DBP matches these widely cited validation criteria, making it the best answer. The other options describe scenarios with larger allowable errors, which would not meet the validation standard.