Activities

Preceding Activity

Estimated Duration in Days

Mean Time

Variance

a

m

b

A

None

$3$

$6$

$15$

$7$

$4$

B

None

$2$

$5$

$14$

$6$

$4$

C

A

$6$

$12$

$30$

$14$

$16$

D

A

$2$

$5$

$8$

$5$

$1$

E

B

$3$

$9$

$26$

$11$

$14\mathrm{.}69$

F

D

$3$

$6$

$15$

$7$

$4$

G

C

$5$

$11$

$17$

$11$

$4$

H

E

$4$

$19$

$28$

$18$

$16$

I

G

$1$

$4$

$7$

$4$

$1$

What is the standard deviation using the above information?