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14. Project Management

14. Project Management

作者: Novazyyy | 来源:发表于2017-10-08 06:29 被阅读33次

1. Project:

Unique one-time operations designed to accomplish a set of objectives in a limited time frame

2. Planning Fallacy: 

people tend to underestimate the time/cost of the task

To avoid Planning Fallacy, you need to break down the entire project into small chunks, which are small enough to accurately estimate the time to complete.

3. What Project Management Can Do

-Answer the time to complete the project

-Answer the scheduled start and end times for each activity

-Find critical tasks (i.e, which activities are critical and must be completed exactly as scheduled in order to keep the project on schedule)

-Find slacks (i.e., how long noncritical activities can be delayed before they cause an increase in the completion time for the project)

4. Tools in Project Management

PERT: Program Evaluation and Review Technique

CPM: Critical Path Method

5. Terminologies Used in PERT/CPM

Activities: Project steps that consume resources and/or time.

Events: The starting and finishing of activities.

Network (Precedence) Diagram: Diagram of project activities that shows sequential relationships by use of arrows and nodes.

Activity-On-Arrow: Network diagram convention in which arrows denote activities.

Activity-On-Node: Network diagram convention in which nodes denote activities.

6. Two Cases When Estimating Time

Deterministic: Time estimates for activities are fairly certain.

Probabilistic: Estimates of activity times that allow for variation.

7.  steps

1st Step:�Decompose Project into Small Tasks

2nd Step:�Identify Dependencies of Small Tasks

3rd Step: Forward Pass

ESi = earliest start time for an activity i

EFi = earliest finish time for an activity i

ti = activity time for activity i

EFi = ESi + ti

Forward Pass: Part of the PERT/CPM procedure that involves moving forward through the project network to determine the earliest start and earliest finish times for each activity.

Earliest Start Time Rule: The earliest start time for an activity is equal to the largest of the earliest finish times for all of its immediate predecessors.

4th Step: Backward Pass

Latest Start Time: The latest time an activity may begin without increasing the project completion time.

Latest Finish Time: The latest time an activity may be completed without increasing the project completion time.

Backward Pass: Part of the PERT/CPM procedure that involves moving backward through the network to determine the latest start and latest finish times for each activity.

Latest Finish Time Rule: The latest finish time for an activity is the smallest of the latest start times for all activities that immediately follow the activity.

8. PERT/CPM Output Terms

Path: A sequence of connected activities that leads from the start to the finish.

Critical Path: The longest path in the project network; determines expected project duration.

Critical Activities: The activities on the longest path in the network.

Slack: The length of time an activity can be delayed without affecting the project completion time.

9. Slacks are interdependent: If one task used up all slack time, then other tasks on the same path may have zero slack time even if slacks are indicated on those tasks.

10. Reduce the Completion Time

-Check to see if the immediate predecessor relationships can be modified so that activities on the  critical path can be performed in parallel.

-Add additional resources to the critical path activities to shorten the length of the critical path.    This is known as crashing.

11. PERT/CPM Probabilistic Model

Optimistic Time t(i)o: The minimum activity time if everything progresses ideally.

Most Likely Time t(i)m: The probable activity time under normal conditions.

Pessimistic Time t(i)p: The maximum activity time if significant delays are encountered

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