Question

The mean square deviation of a set of n observations about points -2 and 2 are 18 and 10 respectively. The standard deviation of the set is

• A. \(3\)
• B. \(2\)
• C. \(1\)
• D. None of these

Hint:

Mean square deviation = variance + square of shift.

Answer 1

The Correct Option is A

Let mean =μ, variance =σ². σ²+(μ+2)²=18, σ²+(μ-2)²=10 Subtracting, 8μ=8⟹ μ=1 σ²=10-(1-2)²=9⟹ σ=3