Answer
$σ_X=2.23$ people.
Work Step by Step
$σ_X=\sqrt {Σ[x^2.P(x)]-μ_X^2}=\sqrt {0^2\times P(0)+1^2\times P(1)+2^2\times P(2)+3^2\times P(3)+4^2\times P(4)+5^2\times P(5)+6^2\times P(6)+7^2\times P(7)+8^2\times P(8)+8^2\times P(8)+9^2\times P(9)+10^2\times P(10)+11^2\times P(11)+12^2\times P(12)-4.87^2}=\sqrt {0\times0.011+1\times0.035+4\times0.089+9\times0.150+16\times0.186+25\times0.172+36\times0.132+49\times0.098+64\times0.063+81\times0.035+100\times0.019+121\times0.004+144\times0.006-23.7169}=2.23$
