Chapter 6 - Section 6.1 - Assess Your Understanding - Applying the Concepts - Page 330: 17d

$σ_X=1.74$ televisions

$σ_X=\sqrt {Σ[x^2.P(x)-μ_X^2]}=\sqrt {[0^2\times P(0)+1^2\times P(1)+2^2\times P(2)+3^2\times P(3)+4^2\times P(4)+5^2\times P(5)+6^2\times P(6)+7^2\times P(7)+8^2\times P(8)+9^2\times P(9)]-3.21^2}=\sqrt {0\times 0+1\times 0.161+4\times 0.261+9\times 0.176+16\times 0.186+25\times 0.116+36\times 0.055+49\times 0.025+64\times 0.010+81\times 0.010-10,3041}=1.74$