Answer :

Solution :

σ₁, σ₂, ...., σ₈, σ₉ = 3

σ_cp = $\sqrt{{\sigma }_1^2+{\sigma }_2^2+\dots +{\sigma }_8^2+{\sigma }_9^2}$

σ_cp = $\sqrt{3^2+3^2+3^2+3^2+3^2+3^2+3^2+3^2+3^2}$

σ_cp = $\sqrt{9\times 9}$ = 9

∴ the standard deviation of the critical path is 9.