Schedule Planning

Types of Dependencies

1. Mandatory dependencies 2. Discretionary dependencies 3. External dependencies

Network Diagram

A network diagram depicts the project activities and the interrelationships among these activities.

Predecessor

A predecessor activity is one that comes before another activity.

Successor

A successor activity is one that comes after the activity in question.

Activity Duration

Activity duration is the process of estimating the time to complete each item on the activity list. The most common measurements used to define durations are days of weeks, but you can also use hours, months, or other increments of time, depending on the project.

Activity Sequencing

Activity sequencing is the process of identifying dependency relationships between project activities and sequencing them in proper order. First you need to identify the type of dependency, and then you need to determine the specific relationship between the activities.

Analogous Estimating / Top-Down Estimating

Analogous estimating (top-down estimating) is the use of actual durations from similar activities on a previous project. This is most frequently used at the early stages of project planning, when yo have limited information regarding the project. Although analogous estimating can provide a good approximation of task duration, it is typically the least accurate means of obtaining an estimate. No two projects are the same, and there is the risk that the project used to obtain the analogous estimates is not as similar as it appears.

Crashing

Crashing is a technique that looks at cost and schedule trade-offs. Crashing is typically implemented by adding more resources to the critical path tasks in order to complete the project more quickly.

Dependencies

Dependencies are relationships between activities. For example one activity may not be able to start until another has finished, or perhaps one activity is dependent on another activity starting before it can finish.

Duration Compression

Duration compression are techniques that can be used to shorten planned duration of the project or during project execution to help resolve schedule slippage. The two duration compression techniques are crashing and fast tracking.

Estimating Techniques

Estimating techniques: 1. Analogous estimating, or top-down estimating. 2. Expert judgement 3. Parametric estimating 4. Three-point estimates 5. Program evaluation and review technique (PERT)

Expert Judgment

Expert judgment uses the people most familiar with the work to create the estimate. Ideally, the project team member who will be doing the task should complete the estimate. If all team members haven't been identified yet, go recruit people with expertise for the tasks you need estimated.

Fast Tracking

Fast Tracking is performing two tasks in parallel that were previously scheduled to start sequentially.

Finish-to-Finish

Finish-to-Finish - Predecessor activity must finish before the successor activity finishes.

Finish-to-Start

Finish-to-Start - Successor activity cannot begin until predecessor has completed activity.

Logical Relationships

Four possible logical relationships can exist between the predecessor activity and successor activity. Identifying the correct relationship between dependent activities is critical to developing an accurate schedule. Depending on the type of dependency relationship, you may be able to schedule the activity in parallel, or the successor activity may have to wait until the predecessor is completed.

Critical Path Method

One of the most widely used techniques in Schedule Development is the critical path method (CPM). CPM determines the amount of float time for each activity on the schedule by calculating the earliest start date, earliest finish date, latest start date, and latest finish date for each. Float is then calculated to determine the amount of time you can delay the earliest start of an activity without delaying the ending of the project. Activities with zero float are considered critical path activities. If a critical path task does not finish as scheduled , the project end date will be affected. The critical path is the longest full path on the project.

Precedence Diagramming Method (PDM)

PDM uses boxes to represent the project activities and arrows to connect the boxes and show the dependencies.

Parametric Estimating

Parametric estimating is a quantitatively based estimating method that multiplies the quantity of work by the rate. To apply quantitatively durations, you must know the productivity rate of the resource performing the task or have a company or industry standard that can be applied to the task in question.

Program Evaluation and Review Technique (PERT)

Program evaluation and review technique (PERT) is a method that the USN developed in the 1950s. PERT and three-point estimates are similar techniques. The difference is that three-point estimates use an average estimate to determine project duration, while PERT uses what's called expected value (or the weighted average). Expected value is calculated using the three-point estimates for Activity Duration and then finding the weighted average of those estimates. The formula to calculate expected value is as follows: (optimistic + pessimistic + (4 x most likely)) / 6

Start-to-Finish

Start-to-Finish - Predecessor activity must start before successor activity can finish.

Start-to-start

Start-to-start - Predecessor activity depends on starting before the successive activity can start.

Float

The final step in determining the critical path is to calculate float for each activity on the network diagram. Float is determined by subtracting the early start from the late start or the early finish from the late finish for each activity.

Forward Pass

The first step in determining your critical path is to complete forward pass thorough the network diagram. This means that you are working from the left to the right of your network diagram. This will give you to calculations for each activity: early start and early finish. Early start is the earliest date activity can begin, as logically constrained by the network. Early finish is the earliest date an activity can finish, as logically constrained by the network.

Defining Activities

The foundation for developing a project schedule is a list of the activities required to complete the project. Activity definition is the process of breaking down the work packages from the WBS into individual activities that make up all the work of the work package.

Backward Pass

The next step to complete the critical path is to complete a backward pass. This means you start at the finish of your network diagram and work back through each path until you reach the start. This gives you two calculations, late finish and late start. Late finish is the latest date an activity can complete without impacting the project end date. Late start is the latest date you can start an activity without impacting the project end date.

Three-Point Estimates

Three-point estimates are an average of the most likely estimate, the optimistic estimate, and the pessimistic estimate for the activity.

Activity List

You'll want to list each activity you've defined on an activity list. This list should include every activity needed to complete the work of the project, along with an identifier or code so that you can track each activity independently. It's also good practice to list the WBS code this activity is associated with, along with a scope of work definition. Once you have all your activities defined, you're now ready to start putting them into the sequence in which they will be completed.