What is the best approximation of the true value after bias has been corrected?

• A. The median
• B. The mode
• C. The geometric mean
• D. The arithmetic mean

Answer: (D)

When bias has been corrected, the remaining errors are random and centered around zero. With several measurements of the same quantity, the arithmetic mean uses all the data points, and under typical measurement error assumptions (independent, identically distributed additive errors), it has the smallest variance among unbiased estimators of the true value. That makes it the most reliable single estimate of the true value.

The median can be more robust to outliers but is less efficient for normally distributed errors. The mode isn’t a stable general estimator for a fixed true value from noisy data, and the geometric mean suits multiplicative or highly skewed data, not additive measurement errors around zero.