Diagramming the Causes of Project Risks

Drop a stone into a pond, and ripples will spread out from the point of impact. This is a cause-and-effect relationship. The rippling effect is caused by the impact of the stone. Remove the cause, and there is no effect.

As a project manager, it is to your advantage to identify the cause of a risk. When you know the cause, you can manage the effect—or risk—appropriately.

One way to view causes and risks is through a flowchart. Flowcharts focus on the cause of the risk instead of on the risk itself. With a contingency plan, you can limit or eliminate a risk's impact on a project's outcome.

The design of a cause-and-effect diagram, which is also called a fishbone or Ishikawa flowchart, is ideal for identifying and showing the possible causes of project risks. It is a diagram that clearly shows the relationship between a risk's cause and its effect.

There is a reason behind every risk—something has to cause a risk to occur. Accurately categorizing the causes for a particular risk will help you to build an effective cause-and-effect diagram.

Risks typically fall into one of six categories:

1. Methods - These risks involve a company procedure or a way of performing a particular task. For example, a company's security policies may not be stringent enough.
2. Materials - These risks involve the supplies a company uses to complete a project. For example, the computers used in a project may not have adequate memory capacity.
3. Environment - These risks involve activities that occur in the immediate physical surroundings. For example, poor weather conditions during a construction project may delay deadlines.
4. People - These risks refer to actions taken by the employees involved in a given project. For example, inadequately trained staff may be a project risk.
5. Information - These risks involve knowledge of a specific event or situation during a project. It can also refer to a lack of documentation or incorrect data. For example, a client's request is not recorded properly in the product specification.
6. Machinery - These risks involve machinery that can be a source of risk in manufacturing. For example, an outdated barker in a paper manufacturing company can be a risk.

These are three steps for constructing a cause-and-effect diagram:

• Identify the risk.
• Identify the causes.
• Build the diagram.

In identifying the risk, you place a concise statement of the problem or effect in a box at the end of a horizontal line.

Once you have identified a risk, you can identify its causes in a brainstorming session. Discussions of this sort typically focus on risks inherent in methods, materials, people, information, machines, and environment.

To build the diagram, you organize the causes of risk into the diagram layout. Each branch represents cause types such as materials, machines, and people.

What are some of the advantages of using a cause-and-effect diagram during the risk identification process? A cause-and-effect diagram acts as a visual display so problems can be seen more clearly. The diagram also helps break large problems down into manageable parts.

Cause-and-effect diagrams are an important part of project planning. In addition to helping you identify risks, these diagrams reveal the causes behind risk so you can manage the risk more effectively.

An Introduction to Trend Analysis

In project management, it is useful to discern trends in the quality data to determine if the project is progressing according to quality expectations. Trend analysis is a technique that tells project managers whether quality goals are being achieved according to the quality management plan.

Trend analysis is a mathematical technique using statistical methods that provide an equation that best fits data in a scatter diagram. Scatter diagrams are simple X and Y axis diagrams with an independent variable, such as time, as the X axis, and the dependent variable as the Y axis. Trend analysis determines the best or most appropriate equation and measures the fit of the equation to the data. Trend analysis is also known as "curve fitting."

Fitting a curve is often done by the least squares method, a mathematical method in which the distance between the data points and a possible line is minimized over its length. This gives the most statistically accurate representation. These lines are often called "regression lines."

Trend analysis is a useful tool for cost and schedule performance, and quality control. The utility of the trend analysis is that it gives a clear and understandable indication of change caused by every incremental change of the independent variable. One of the more useful functions of trend analysis is predicting, or forecasting.

The different lines mean a variety of different things could have occurred in a process. Line and curve shapes indicate whether a process is behaving according to the quality control norms.

• Lines of positive correlation - Lines of positive correlation indicate the desired value y is increasing. This is good if improvement is sought, but bad if the line continues past a specified value.
• Lines of negative correlation - Negative correlation indicates y is decreasing. This is good if the tolerance of a process is coming closer to a desired value, but bad if that same value is exceeded.
• No correlation - A diagram with no correlation means the data is inconsistent. The process is out of control, and immediate steps are necessary to bring the process under control.
• No slope lines - A line with no slope means there is no change. This is indicative of a stable process.
• Curvilinear line - Curvilinear lines indicate a cyclical process or a process decreasing or increasing at a non-uniform rate. Cyclical patterns indicate a possible worn out process. A curvilinear line indicates a complex relationship with the independent variable.

Of all the different lines, curved lines are the most difficult to make conclusions from because of their shape. Other statistical analysis must be used to determine at which point the objective value has been met or exceeded.

Trend analysis allows project managers and teams to predict a pattern and come up with a formula that accurately reflects a data set. As long as the appropriate quantity of data have been selected, accurate predictions can be made of a process. Trend analysis is also useful for determining at which point a quality concern may become an issue based on historic data. Trend analysis is often useful when used in conjunction with other tools and techniques.

An Introduction to Pareto Diagrams

Do you need a simple chart to convey the idea that quality corrective action is required? Pareto diagrams offer an effective, illustrative, and analytical tool for identifying quality problems.

A Pareto diagram is a modified histogram performance report. It receives its information from work results such as data figures, repair data, maintenance figures, or scrap rates.

Instead of grouping results by intervals as in histograms, Pareto diagrams lump similar quality defects together in order to identify the most common errors for corrective action. This is based upon the 80/20 rule where 80 percent of the defects are caused by 20 percent of the problems. Pareto diagrams are useful for measuring machine output and time reliant processes. There are three uses and types of Pareto diagrams.

• Basic Pareto analysis - A basic Pareto analysis identifies the key contributors to the quality problem as a single diagram, with a percentage line showing each category as a portion of the cumulative total. The basic Pareto diagram identifies the most common problems.
• Comparative Pareto analysis - A comparative Pareto analysis looks at a problem as a "before and after" comparison, using two Pareto diagrams. These diagrams show the change in the number of problems identified for each problem category.
• Weighted Pareto analysis - Weighted Pareto analysis gives significance to unapparent factors such as cost, time, or criticality.

Once a Pareto diagram is constructed, the key defect areas become obvious, so you can reduce these defects to a more acceptable level. Then, after implementing corrective action, a new Pareto diagram may be constructed as a comparison to show that the key defects were greatly reduced.

Pareto diagrams are an extremely useful tool in quality decision making. The diagrams make it clear what quality changes need to be made and whether the remedy was effective. Keep in mind that Pareto diagrams do not identify causes, only problems, so other analytical methods may be required to gain further insight into the problem.

Constructing Cause-and-effect Diagrams

Have you ever had a quality problem that couldn't be quantified through the use of statistics? The relationship between a problem's effect and its cause is sometimes obscure. To solve the problem, you may need to examine the entire process, identifying all the potential problem sources before you can determine the root cause. When visually displayed, this problem-identification process is called cause-and-effect diagramming.

Cause-and-effect diagrams are also known as "wishbone" or "fish" diagrams because of their shape. A cause-and-effect diagram has a central "back bone" with "ribs" branching off. The process used to create the diagram is known as flowcharting.

Cause-and-effect analysis is frequently completed by a team since specialists in many areas or departments may be required to provide input into their part of the process. During a project meeting or conference, the project team will construct the diagram, starting with the problem and working backward to the beginning of the project or process.

In cause-and-effect diagramming, there are three possible methods for identifying causes:

1. the random method
2. the systematic method
3. the process analysis method

The random method, during which team members randomly cite problems and probable causes, is a somewhat haphazard approach and may not identify all problem categories. However, it is useful as a general trouble-shooting technique and can help get the group in problem-solving mode.
The other two methods, systematic and process analysis, are more structured and rational in the identification of causes. These are used mostly by engineers and technicians.

The systematic method focuses analysis on one category at a time. Each category is examined in descending order of importance after the primary one is addressed.

The process analysis method looks at a production process identifying each sequential step, and the categories and causes for each step, one at a time.

When the cause-and-effect diagram has been constructed, the team or project manager can then suggest changes to the potential problem-causing areas. A series of experiments or additional statistical analysis may be necessary to determine the primary or root cause of a given problem.

The next step is to decide what corrective action is necessary. In the process of identifying the problem, the team suggests the desired outcome. By turning the diagram around, you can determine what impact the desired outcome will have on each of the listed categories and causes. In some cases you may find corrective action is required in one or all of the categories.

A machine in a process may require finer adjustment or even replacement if worn out. A newer machine may offer a leap in technology that may eliminate present quality control problems through greater automation or internal computer control processes.

The production or process method may require fine tuning, involving additional substeps before completion of a task. The layout of a process may also need reorganizing. Duties and responsibilities may need increased emphasis.

Stricter inspection and handling of raw materials may be necessary to ensure that they are of high standard. Improved selection of raw materials may also be required.

Changes to the measurement process may be necessary, such as more accurate measurements, increased frequency of inspection, and introduction of new statistical methods for analysis.

Perhaps current personnel are inadequately trained in both their job and in quality control. Upgrading job skills may be necessary. It is also possible that declining quality is due to poor work habits or boredom with the job.

Once the root cause of the problem has been identified and the effects of the desired outcome on other areas of the project have been studied, appropriate corrective action is taken. At this point, change requests are processed and safeguards set in place to prevent future recurrences.

Even when a problem has multiple sources, you will find cause-and-effect diagrams are invaluable in pinpointing them all. Flowcharting with cause-and-effect diagrams is an effective way to conceptualize causes to a problem in a project or process. Once flowcharted, the problem can be further analyzed using other analytical tools. Ultimately, corrective action and protective safeguards are applied to solve the problem and prevent future recurrences.

Presenting Schedule Information Graphically

Everyone follows a schedule of some sort—a meal schedule, an exercise schedule, or a meeting schedule. In the area of project management, a schedule includes a list of project activities along with the planned start and expected finish dates for each part of the activities. This schedule may be presented in summary form or in detail using either a tabular or graphical format.

The tabular format presents the information in a table. The tabular format is very rarely used, as the information it presents is hard to read and understand.

The graphical format presents the information in the form of a diagram or chart. It allows the project manager to visualize the schedule.

When it comes to presenting schedule information graphically, you have a number of choices. The most common graphical presentation formats are the project network diagram (PND), Gantt chart, milestone chart, and time-scaled network diagram.

A project network diagram (PND) is a schematic display of the project's activities and the logical relationship between them. Each planned activity is numbered on the PND. For example, the number 1 could be Activity 1—the architecture and design of the project. Number 2 could then be the foundation work.

A Gantt or bar chart is the most convenient, commonly used, and easiest-to-understand format of data presentation for project planning, resource scheduling, and status reporting. It shows start and finish dates as well as the expected durations for each project activity.

A milestone chart is a summary-level schedule that identifies the major activities or deliverables of the project. It can become the skeleton for the master schedule. A milestone typically marks the end of an event or the completion of an activity.

A time-scaled network diagram is a cross between a Gantt chart and a PND. It displays the project logic, activity durations, and schedule information. The positioning and length of the activity arrow represent its duration.

Remember, there are a number of formats that your company may choose from when creating a project schedule. Determine the individual needs of your project and the key stakeholders, then make your choice based on those needs.

Three Ways to Diagram Projects

Before leaving on a trip you gas up the car and then check the road map for the best route. Project managers also have road maps that they can follow to choose the best route for their projects.

The project network diagram, also known as a project manager's road map, is one of the inputs to schedule development. It is a schematic display of the project's activities and their logical relationships or dependencies. It may be produced manually or on a computer, and may include full project details, or have one or more summary activities. The diagram should be accompanied by a summary narrative that describes the sequencing approach.

Project managers use three principal types of network diagrams: precedence diagramming method (PDM), arrow diagramming method (ADM), and conditional diagramming method (CDM).

Precedence diagramming method (PDM)
The precedence diagramming method (PDM) uses nodes to represent activities. Arrows join the nodes together and indicate the dependencies between activities. This technique is also known as activity-on-node (AON) and is the method most widely used by project management software.

The precedence diagramming method is based on four types of dependencies: finsh-to-start, finish-to-finish, start-to-start, and start-to-finish. The first activity in a dependency relationship is referred to as the "from" activity. The second is referred to as the "to" activity.

• In a finish-to-start dependency the "from" activity must finish before the "to" activity can start. For example, on a courseware development project, you must finish the scripting before the graphics can be developed.
• In a finish-to-finish dependency, the "from" activity must finish before the "to" activity can finish. For example, car body and engine production can be started at the same time. The last step in the engine production phase is to install it in the body. Therefore, the body must be finished before the engine can be finished.
• In a start-to-start dependency, the "from" activity must start before the "to" activity can start. For example, on a telemarketing project the compilation of phone lists must be started before people can actually be called.
• Finally, in a start-to-finish dependency, the "from" activity must start before the "to" activity can finish. For example, if your car refuses to start, you may need to jump start the battery with booster cables. The engine must start before you can finish jump starting the car.

In the precedence diagramming method, finish-to-start is the most commonly used type of dependency.

Arrow diagramming method (ADM)
The arrow diagramming method (ADM) uses arrows to represent the activities and connects them at nodes to show dependencies. This technique is also known as activity-on-arrow (AOA). Although less common than the PDM, it is still the technique of choice in some application areas.

In an ADM, "dummy activities" are used to show logical relationships when logical relationships cannot be completely or correctly described with regular activity arrows. A dummy activity uses no resources, has a duration of zero, and is represented by a dashed arrow.

Conditional diagramming method (CDM)
The conditional diagramming method (CDM) allows you to diagram activities that must be repeated more than once. This technique also allows you to diagram non-sequential activities. The two most widely used techniques for creating a CDM are graphical evaluation review technique (GERT) and system dynamics.

Activities that must be repeated more than once are known as loops and can affect the project schedule if their durations are not calculated properly. An example of a loop may be the testing component of a project that needs to be repeated more than once.

When your project has an activity that only occurs under the right conditions, you will need to add conditional branches to the schedule. For example, a conditional branch may be added following an inspection activity. This would indicate that if errors are detected in the product, changes to the product's design may be needed.

Project managers use standardized network diagrams to create project network diagrams faster than they could by drawing them out using a pen and paper. These networks can include an entire project or only a portion of it. Portions of a network are commonly referred to as subnets or fragnets. Subnets are especially useful when a project has several identical or near identical features. Examples of subnets include constructing floors in a high-rise office building, or doing clinical trials on a pharmaceutical project.

Project network diagrams can be used as a guide for your project team and to help your management team better monitor project progress. This ultimately increases your chances of executing a successful project.

Project Activity Sequencing Outputs

Project activity sequencing consists of the methods and tools used to set the stage for the most efficient and trouble-free project plan. Project activity sequencing has several outputs, including the project network diagram and activity lists.

The project network diagram
One output that results from activity sequencing is the project network diagram. This diagram may be produced manually or on a computer.

The project network diagram includes full project details, including clear, concise, self-explanatory names for all project activities.

Full project details include "hammock activities" as well. For example, an auto parts manufacturer inspects all the parts it produces. Rather than repeat the inspect activity in the project network diagram, the manufacturing company rolls all inspection into a single summary or hammock activity.

Overall start and finish dates are then associated with the single hammock activity. One or more summary or hammock activities often make up part of full project details.

The project network diagram includes a summary narrative. The summary narrative outlines the basic activity sequencing approach used in the network. The summary narrative provides details about the use of dependencies, sequencing assumptions and leads and lags.

The summary narrative outlines how dependencies are included in the project, how outside dependencies will be handled, and which dependencies are mandatory or optional.

The summary narrative also includes assumptions about sequencing. It may be assumed, for example, that testing can start after 25 percent of development has taken place.

In addition to assumption, the summary narrative outlines how leads and lags will be handled. In a finish-to-start relationship, an activity with a lead of five days may start five days before its predecessor has finished. An activity with a lag of five days cannot start until five days after its predecessor activity has finished.

Finally, the project network diagram contains a description of unusual sequencing. Unusual sequences occur in a network to allow for things like client preferences or specific resource availability. For example, in setting up a computer network, it may seem logical to configure the servers before configuring the workstations. The customer, however, may stipulate that employees are to begin training and work on their workstations immediately. As a result, the configure workstations activity takes place in the project network diagram before the configure servers activity.

Activity list updates
The second output from activity sequencing is activity list updates. Network diagram preparation may reveal instances where an activity must be divided or redefined in order to diagram the correct relationships.

As an example, consider the initial activity list for installing a computer network. Attempts to construct a network for this project reveal that there is overlap between the build and test activities. Computer tower components must be tested at intermediary intervals.

If the build and test activities have been defined at too high a level, the sequencing diagram may not show this overlap. The solution is to break the build and test activities down into their component parts, and indicate their dependencies on other activities. Based on this, a new project network diagram can be constructed.

The outputs from activity sequencing are the project network diagram and the activity list. These two outputs are important components in the creation of the project schedule. The project network diagram reflects project activities and their dependencies. After initially diagramming the network, the activity list may remain the same or change based on the diagram.

Conditions for Using a Network Diagramming Template

Think about building a house when all the pieces are already prepared. You're only responsible for assembling the parts and making minor adjustments. Once you build the first house, you can use the pattern to build others.

Network diagram templates, like prefabricated houses, are standardized, pre-built components. They allow you to use successful past projects as models for the current project and schedule planning activities. Using network diagram templates helps you improve the accuracy of activity sequencing by highlighting successful practices from past projects.

Network diagram templates help you complete your work more quickly because much of the work has already been done for you. Using the successful elements from past projects also saves money on the overall current project.

Finding similarities between past and current projects is extremely helpful in planning and activity sequencing. It is appropriate to use network diagram templates as a tool for activity sequencing, when there are similarities between overall projects and among subprojects in larger projects.

• Similarities between projects - The first situation in which you should consider using network diagram templates as a tool for activity sequencing is when similarities between two separate projects are identified. Some similarities between projects include phases and deliverables. Effective network diagram templates cover the entire project and are especially useful when the past and current projects share a common structure.
  
  Consider the following example. Jack, the training director for a large engineering firm, is responsible for the continued development of in-house training courses. Since each training course has the same design cycle, Jack is able to use network diagram templates for activity sequencing of these internal courses.
  

• Similarities between subprojects - The second situation in which network diagram templates are useful is when there are similar features within a single project. These features are often called subprojects or subnets. Subnet templates are useful for projects where there are several identical features within the work breakdown structure. After completing a network diagram for the first subnet, you can use it as a template for other components within the same project.
  
  It is best to use subnet diagram templates with projects that have repetitive phases, such as floors in a high-rise building, clinical trials in pharmaceutical research, or program modules in a software project.
  

Network diagram templates can help you save time by reducing the duplication of effort where similarities between projects and subprojects exist. Understanding when to use diagramming templates will allow you to reach project goals more quickly an

Publish Post

d efficiently.

Conditional Diagramming Method (CDM)

A third technique for constructing network diagrams is the conditional diagramming method (CDM).

Like other diagramming methods, the CDM uses nodes and arrows to represent the activities and dependencies in a project network. However, this method is distinguishable from other diagramming techniques by its loops and conditional branches.

Loops seen in the CDM indicate the repetition of activities in the activity network.

Conditional branches indicate options in a CDM diagram. The truth or falsity of a condition determines whether contingent activities will happen next.

For example, one phase of auto manufacturing involves painting the auto body. The activities that make up this phase may be outlined in the CDM diagram. In this case, the pass or fail condition of the painted auto body determines whether the auto body is delivered or redone. Delivering the auto body or redoing it are conditional branches or options dependent on the outcome of the pass/fail test.

In project management, the diagramming technique known as Graphical Evaluation and Review Technique (GERT) uses the CDM.

The conditional diagramming method is a technique that represents a network and shows the repeating and conditional activities in the project. This technique is valuable for helping you visualize and plan an activity's schedule. Using the CDM will help you to stay in control of the schedule which, in turn, will increase your chances of a successful project.

Arrow Diagramming Method (ADM)

Every project consists of a number of tasks which must be coordinated and scheduled to meet project goals and deadlines. A project planning network is a graphical representation of the overall project. Its graphical elements indicate activity duration and "precedence relationships," the order in which project tasks must be performed.

Various techniques exist for constructing network diagrams. One popular technique is the arrow diagramming method (ADM). The ADM, also known as the activity-on-arrow (AOA) network, uses arrows to represent activities and nodes to show dependencies.

In the ADM, activities are connected at points called nodes. A node preceding an activity arrow is the start event for that activity. A node following an activity arrow is the end event for that activity.

The ADM uses only finish-to-start (FS) activity dependencies. This means that activity A must finish before activity B can begin.

The first thing to remember when using the ADM is that an activity can't be represented by more than one arrow in the network diagram. Suppose activity A precedes two activities in a network. To avoid duplicating activity A on the diagram, you would need to follow one arrow representing activity A by an end node. Then follow this end node for A by the two successor activities, B and C.

The second thing to remember is that no two activities can have the same begin and end nodes. Instead, if two activities are related or dependent, you can use a "dummy" activity to show the relationship. A dummy uses no resources and is represented by a dashed arrow.

In addition to activities and dependencies, the ADM shows the early and late schedules for the project. Both the early time (TE) and the late time (TL) for an event appear on the event node.

The ADM also allows project managers to specify activity scheduling flexibility by calculating "float." Float is the amount of time available to complete an activity without affecting project duration. To determine a project activity's float, or slack, you would calculate the difference between the activity's late and early schedule times.

Once float has been determined for each event in the network, it is possible to find the critical path through that network. The critical path shows the earliest possible completion time of the entire project. To find the critical path in an AOA network diagram, you would follow the path that connects all events with zero float since activities with a positive float are, of necessity, not on the critical path.

The arrow diagramming method is a method used to construct network diagrams. Arrow diagramming is said to be "event-oriented" because the arrows represent activities. Arrow diagramming reveals the network sequence and timing of activities which is useful in managing the project's schedule.

Precedence Diagramming Method (PDM)

A project is a series of interconnected activities that can be represented by the project network diagram. Various techniques exist for constructing network diagrams. One of the most common is the precedence diagramming method (PDM).

The PDM uses nodes to represent project activities and connecting arrows to show activity dependencies. This technique is also called the activity-on-node (AON) network approach.

To construct a network diagram, you need to consider four types of precedence relationships: finish-to-start (FS), start-to-start (SS), start-to-finish (SF), and finish-to-finish (FF).

• finish-to-start (FS)
  The FS relationship is one in which activity A must finish before activity B can begin. This is the most commonly used type of precedence relationship.
  

• start-to-start (SS)
  The SS relationship is one in which activity A must start before activity B can start. As an example, let activity A be compiling a phone list, and Activity B be calling the people on the list. In this example, compiling the phone list (A) must start before calling the people on the list (B) can start.
  

• start-to-finish (SF)
  The SF relationship is one in which activity A must start before activity B can finish. Let activity A be breathing on one's own. Let activity B be breathing with the aid of a respirator. Breathing on one's own must start (A) before breathing with the aid of a respirator (B) can finish.
  

• finish-to-finish (FF)
  The FF relationship is one in which activity A must finish before activity B can finish. Let activity A be a telemarketing department compiling a phone list. Let activity B be calling the people on the list. Compiling the phone list (A) must finish before calling the people on the list (B) can finish.
  

To convey as much information as clearly as possible, project network diagrams also include early and late schedules.

• the early schedule
  The early schedule is made up of the earliest start (ES) and earliest finish (EF) times. In a project, the ES for an activity is the earliest possible time that the activity can begin. The EF is the earliest possible time that the activity can end.
  
  You can determine the ES for an activity by looking at its predecessors. No predecessors means that the ES is day one, the beginning of the project. One predecessor means that the ES for the activity is dependent on the EF of the predecessor. More than one predecessor means that the ES of the activity depends on the maximum of the EF times of the predecessor activities.
  

• the late schedule
  The late schedule consists of the latest start (LS) and latest finish (LF) times. In a project, the LS and LF are the latest times that an activity can begin and end without causing project delay.
  
  You can calculate the LS and the LF times by using the early schedule. First, set the LF time of the last activity to the EF time of the same activity. Likewise, you can determine the LF time of all immediate predecessor activities by choosing the maximum of the EF times on all predecessor nodes.
  

Once the early and late schedules are in place, you can determine a float for an activity by taking the difference, LF minus EF.

LF - EF = LS - ES

The activity has no float if this number is zero. Float allows for some flexibility in project management and can change as the project progresses.
In a project network diagram, the series of activities that determines the earliest possible completion of the project is called the critical path. The critical path is usually defined as those activities for which float is zero.

To determine the critical path, begin with the first activity in the project. Look at its successors. Compare the successors' float values. Select the one with zero float. This is the second activity on the critical path.

Continue from the second activity on the critical path and compare the float for its successors. Select the activity that has zero float and include it in the critical path.

Continue this process to the final activity for a complete critical path. Ultimately, a project cannot finish any sooner than the time it takes to complete the activities on the critical path.

The PDM represents a project as a network of interrelated activities. The PDM is a way to prepare project activities for scheduling by organizing them in terms of the project's relationships, early and late schedules, float, and critical path. In this way, the PDM allows you to arrive at a realistic, workable project schedule.