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# Why critical activities not same longets path activities?

2 replies [Last post]
hanson California
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Joined: 9 Jan 2012
Posts: 116

Dear Planners,

I have schedule 7000 activities our clints working on with critical activities 850 and longest path only 5 ... why they are not equal or close to geather?

Thank you,

## Replies

Robert Lowe
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Joined: 16 Sep 2005
Posts: 22
Groups: None

That's because Longest Path is a calculated value and Critical Activities in a schedule may not be on the "Critical Path".

Let's keep this simple. Take a network of seven activities. A start milestone is tied F-S to three activities, each with a value of 1 unit. These three activities are tied to activity 5, F-S. Activity 5 has a value of 1 unit and is tied to Activity 7, a Finish Milestone. Of the three activities, activity 2 is tied to activity 6, F-S. Activity 6 has a value of 5 units. From this example the Longest Path goes 1,2,6,7. Subjectively someone could call activity 5 critical because its fed by 2, 3, & 4. I wouldn't argue with them.

We had a former president that answered a question once, "It depends on what your definition of is, is."

Longest path is calculated. Critical Path is calculated as well, but the value you choose to make those activities are subjective. Critical activities are those activities within the schedule that are "choke points". They are were a series of activities come together. The could be on the critical path, but then they might not be.

My guess is that your client is using Total Float at some value other than 0 to define Critical.

Robert Lowe
Offline
Joined: 16 Sep 2005
Posts: 22
Groups: None

That's because Longest Path is a calculated value and Critical Activities in a schedule may not be on the "Critical Path".

Let's keep this simple. Take a network of seven activities. A start milestone is tied F-S to three activities, each with a value of 1 unit. These three activities are tied to activity 5, F-S. Activity 5 has a value of 1 unit and is tied to Activity 7, a Finish Milestone. Of the three activities, activity 2 is tied to activity 6, F-S. Activity 6 has a value of 5 units. From this example the Longest Path goes 1,2,6,7. Subjectively someone could call activity 5 critical because its fed by 2, 3, & 4. I wouldn't argue with them.

We had a former president that answered a question once, "It depends on what your definition of is, is."

Longest path is calculated. Critical Path is calculated as well, but the value you choose to make those activities are subjective. Critical activities are those activities within the schedule that are "choke points". They are were a series of activities come together. The could be on the critical path, but then they might not be.

My guess is that your client is using Total Float at some value other than 0 to define Critical.