Project Management Scheduling Tools | Project Managing Schedule Variance

Scheduling and scheduling function are one of the important aspects in project management system. A schedule is a timetable for a plan and therefore cannot be established until the plan has been developed Information technology projects require proper project management discipline in order to collect system requirements, design systems and adequately trained users.

When network-planning techniques are used, scheduling depends on the planning function. With projects for which there is a high degree of uncertainty about the activity duration estimates, it is possible to use three duration estimates, an optimistic, a pessimistic, and the most likely. The project schedule control process involves regularly gathering data on project performance, comparing with the planned performance.


The first step in establishing a project is to estimate how long each activity will take, from the time it is started until the time it is finished. This duration estimate for each activity is the time for the work to be done plus associated waiting time. An activity duration estimate must be based on the quantity of resources expected to be used on the activity.


The estimate should be aggressive, yet realistic. Throughout the performance of the project some activities will take longer than their estimated duration, others will be done in less time than their estimated duration, and a few may conform to duration estimates exactly. Over the life of a project that involves many activities, such delays and accelerations will tend to cancel out one another.


In order to establish a basis from which to calculate a schedule using the duration estimates for the activities, it’s necessary to select the estimated start time and required completion time for overall project. To determine this, you can calculate a project schedule that provides a timetable for each activity.


These times define overall window or envelope, of time in which the project must be completed. The projects required completion time is normally part of the project objective and stated in the contract. Once the, estimated duration for each activity in the network and an overall window of time in which the project must be completed, you have to decide whether the activities can be done by the required completion time.


Given an estimated duration for each activity in the network and using the project’s estimated start time as a reference, you can calculate the following times for each activity. The ES and EF are determined by calculating forward that is, by working through the network diagram from the beginning of the project to the end of the project.


(a) Earliest start time (ES): It is the earliest time at which a particular activity can begin. Calculated on the basis of the project’s estimated start time and duration estimates for preceding activities.

(b) Earliest finish time (EF): It is the earliest time by which a particular activity can be completed, calculated, calculated by adding the activity’s duration estimate to the activity’s earliest start time.

(c) Latest finish time (LF): It is latest time by which a particular activity must be completed in order for the entire project to be finished by the required completion time, calculated on the basis of the project’s required completion time and duration estimation of succeeding activities.

(d) Latest start time (LS): It is latest time by which a particular activity must be started in order for the project to be finished by its required completion time, calculated by subtracting the activity’s duration from the activity’s latest finish time.

The LF and LS times are determined by calculating backward that is working through the network diagram from the end of project to the beginning of the project.

(e) Total slack (TS): The total slack for a particular path of activities is common to and shared among all the activities on the path. It is sometimes called float. If total slack is zero, the activities on the path do not need to be accelerated but cannot be delayed. If it positive, it represents the maximum amount of time that the activities o n a particular path can be delayed, if it negative, it indicates lack of slack over the entire project.

(f) Critical path: A project cannot be completed until the longest path of activities is finished. This longest path in the overall network diagram is called critical path.


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