The PERT is a management tool, having expected mean time (tm), optimistic time (t0) and pessimistic time (tp), where the variance is given by ______.
1
\(\frac{{{t_p} - {t_0}}}{6}\)
2
\(\frac{{{t_0} + 4{t_m} + {t_p}}}{6}\)
3
(tp – t0)2
4
\({\left( {\frac{{{t_p} - {t_0}}}{{6}}} \right)^2}\)