Question:hard

For a normal distribution variance of mean V(Mean) and variance of median V(Median), which of the following is true?

Show Hint

For normal populations, \(V(\text{Median}) = (\pi/2)\,V(\text{Mean})\), and \(\pi/2 > 1\).
Updated On: Jul 4, 2026
  • V(Median) < V(Mean)
  • V(Median) = V(Mean)
  • V(Median) > V(Mean)
  • V(Median) &times; 1.57 = V(Mean)
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: Under normality, both the sample mean and sample median are unbiased estimators of the population mean $\mu$.
Step 2: By the Cramer-Rao inequality, the minimum possible variance any unbiased estimator of $\mu$ can achieve is $\sigma^2/n$, and the sample mean actually attains this bound, making it the most efficient (minimum variance unbiased) estimator for a normal population.
Step 3: The sample median is a different, less efficient estimator: its asymptotic efficiency relative to the mean is only $2/\pi \approx 0.637$, meaning it uses information less effectively than the mean.
Step 4: Since the mean already achieves the lowest possible variance and the median is strictly less efficient, the median's variance must be strictly larger: $V(\text{Median}) > V(\text{Mean})$.
\[\boxed{V(\text{Median}) > V(\text{Mean})}\]
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