Chapter 6 - Section 6.1 - Assess Your Understanding - Applying the Concepts - Page 330: 18d

$σ_X=1.175$ activities.

$σ_X=\sqrt {Σ[x^2.P(x)-μ_X^2]}=\sqrt {[0^2\times P(0)+1^2\times P(1)+2^2\times P(2)+3^2\times P(3)+4^2\times P(4)-2.519^2]}=\sqrt {0\times 0.073+1\times 0.117+4\times 0.258+9\times 0.322+16\times 0.230-6.345361}=1.175$