This question was previously asked in

SSC CGL Tier-II ( JSO ) 2018 Official Paper ( Held On : 14 Sept 2019 )

Option 2 : 64

Cell

339239

10 Questions
10 Marks
7 Mins

**Given**

Arithmetic mean = (μ) = 10

Coefficient of variation = CV = 40% or 0.4

**Formula**

**CV = **σ/μ

σ = Standard deviation

μ = Mean

**Calculation**

0.4 = σ/10

**⇒ σ/ = Standard deviation **= 0.4 × 10 = 4

Now, Variance= V = (standard deviation)^{2} = σ^{2}

⇒ Variance = 4^{2} = 16

**We know that V(ax + b) = a ^{2}(V(x)**

⇒ V(10 - 2x) = (-2)^{2 }V(X)

⇒ V(10 - 2x) = 4V(x)

**∴ V(10 - 2x) = 4 × 16 = 64**

__Important Points__

**Symbol of Standard deviation = **σ

Variance = square of standard deviation = σ^{2}

Coefficient of variation = CV = CV = σ/μ

μ = Population mean