A Comprehensive Guide to PERT: Understanding Program Evaluation and Review Technique and Using PERT Charts

PERT, or Program Evaluation and Review Technique, is a project management tool used to plan and schedule projects. PERT charts provide a graphical representation of a project's timeline with tasks displayed as nodes and dependencies shown as arrows between nodes. This comprehensive guide will explain everything you need to know about PERT, from what it is to how to create and use PERT charts for project planning. Read on to become a PERT expert!

What is PERT?

PERT stands for Program Evaluation and Review Technique. It is a project management tool used to plan, schedule, and coordinate tasks within a project. PERT was developed in the late 1950s for the U.S. Navy's Polaris submarine missile program and has been adopted by many industries for project management.

The main purpose of PERT is to evaluate the time and resources needed to complete a project. It does this by creating a network diagram of all the tasks that must be completed. These tasks are represented as nodes on the PERT chart. The connections between nodes are the dependencies between tasks. PERT charts provide a graphical overview of the entire project so you can identify the critical path - the sequence of dependent tasks that determines the total project duration.

Some key things to know about PERT:

• It is a planning tool to schedule complex projects with many interdependent tasks.

• Allows you to determine the minimum time needed to complete a project.

• Uses network diagrams to display tasks, dependencies, and the critical path.

• Calculates time estimates based on optimistic, most likely, and pessimistic durations.

• Helps project managers coordinate tasks and resources efficiently.

• Widely used for major one-time projects rather than routine activities.

In summary, PERT is an essential project management technique for planning, scheduling, and managing complex projects through graphical representations of task sequences and resource dependencies. It provides an critical path to enable efficient project completion.

How to Create a PERT Chart

To create a PERT chart, follow these key steps:

1. List all the tasks in the project. Break down work into small, manageable tasks. Capture every activity from start to finish.

2. Determine dependencies between tasks. Which tasks must be completed before others can begin? Draw arrows to link dependent tasks.

3. Estimate task durations. Provide optimistic, most likely, and pessimistic time estimates for each task.

4. Calculate expected task time. Use the PERT formula to calculate expected time as (optimistic + 4 x most likely + pessimistic) ÷ 6.

5. Determine critical path. The critical path is the longest path of dependent tasks that determines total project duration.

6. Create PERT chart. Use nodes for tasks, arrows for dependencies, and expected durations to draw the PERT chart.

7. Optimize schedule. Review the PERT chart to find ways to shorten time on critical path to reduce project duration.

8. Update PERT chart as project progresses to track actual vs planned schedule.

Following these steps will allow you to create a detailed PERT chart that provides a master schedule for your project and enables monitoring of progress. Let's look at each step in more detail.

List All Project Tasks

The first step is to identify all the work required to complete the project. Break down the project into distinct tasks and activities. Get into the details - try to capture every single task from start to finish.

For example, if the project is to launch a new website, the tasks may include:

• Conduct market research

• Create website content

• Write code for web pages

• Develop site navigation

• Create graphics and visuals

• Integrate with database

• Test website functionality

• Launch live site

• Market website

The goal is to decompose the project into manageable pieces of work that can be estimated and scheduled. Each task should represent work that can be assigned and completed.

Determine Task Dependencies

Once you have a complete activity list, determine the dependencies between tasks. Some tasks must be completed before others can begin. These dependent tasks are linked together in a sequence.

For example, software code must be written before testing can begin. Site content must be created before visual designs are made. Identify these dependencies between tasks and draw arrows on the PERT chart to indicate the links.

PERT charts have four types of dependency relationships:

• Finish to start: Task 2 can't start until Task 1 finishes.

• Finish to finish: Task 2 can't finish until Task 1 finishes.

• Start to start: Task 2 can't start until Task 1 starts.

• Start to finish: Task 2 can't finish until Task 1 starts.

Dependencies create the workflow that must be followed to complete a project sequentially from start to finish.

Estimate Task Durations

Once all tasks and dependencies are mapped out, the next step is to estimate how long each task will take to complete.

PERT uses three time estimates for each task:

• Optimistic time (O) - Shortest time needed if everything goes perfectly.

• Most likely time (M) - Realistic time estimate based on normal effort.

• Pessimistic time (P) - Longest time needed for task completion.

These estimates provide a range of possible durations to account for uncertainties in how long tasks may actually take.

Calculate Expected Task Time

After the three time estimates are determined for each task, the PERT formula is used to calculate the expected time duration for each task:

Expected time = (Optimistic + 4 x Most likely + Pessimistic) ÷ 6

Some key points on expected duration:

• Weights the most likely estimate more heavily.

• Attempts to account for uncertain durations.

• Used as the standard time estimate for a task in the PERT chart schedule.

Calculate the expected time for each task using the PERT formula. This provides the task durations you'll use for the PERT chart.

Determine the Critical Path

The critical path is the longest sequence of dependent tasks that determines the total project duration. It is the path through the network diagram from start to finish with the longest total expected time.

To find the critical path:

• Add expected durations for each path of tasks. 

• The path with the longest total time is the critical path.

The critical path highlights the most important tasks that must be completed on time to achieve the project deadline. If critical path tasks are delayed, the whole project will be delayed.

Create the PERT Chart

With all the information gathered in previous steps, you can now create the PERT chart. The PERT chart provides a graphical overview of the project schedule including:

• Task nodes

• Task dependencies

• Expected task durations

• Critical path

Having all key tasks, time estimates, and critical path mapped out in one view provides an actionable project schedule. The PERT chart is a roadmap for executing the project on time.

Optimize the Schedule

Once the initial PERT chart is created, review it to identify opportunities to optimize the schedule. Look for ways to shorten durations on critical path tasks to reduce total project length. For example:

• Add resources to critical tasks for faster completion.

• Break large tasks into stages for overlapping work.

• Reduce time delays between dependent tasks.

• Complete tasks in parallel where dependencies allow.

Optimizing the schedule can help you meet project deadlines and complete projects faster. PERT charts make it easy to visualize schedule improvements.

Update PERT Chart

As the project progresses, update the PERT chart to reflect actual start/finish dates and task durations. Track when tasks are completed and monitor the impact on downstream dependencies.

Use the updated PERT chart to re-forecast the project finish date based on progress. Identify new critical paths based on actual performance. The chart serves as an early warning system for schedule overruns.

By continually updating the PERT chart, it serves as a project control tool to manage work accomplishment versus the plan.

In summary, following this eight step process allows you to create an effective PERT chart to plan, schedule, monitor, and control project activities. Mastering PERT methodology is essential for successful project management.

PERT Chart Example

Let's look at an example PERT chart using the steps outlined above. Imagine we need to plan a project to create and launch a new mobile app.

Here are the key steps involved:

1. List Tasks

• Conduct market research

• Define app features

• Write code modules

• Create visual designs

• Develop marketing plan

• Build app

• Test app

• Fix bugs

• Submit app to app stores

• Market app launch

2. Determine Dependencies

• Market research → Define features

• Define features → Write code

• Write code → Create designs

• Create designs → Build app

• Build app → Test app

• Test app → Fix bugs

• Fix bugs → Submit to app stores

• Submit to app stores → Market launch

3. Estimate Task Times

TaskOptimisticMost LikelyPessimisticMarket research2 weeks4 weeks8 weeksDefine features1 week2 weeks4 weeksWrite code4 weeks8 weeks16 weeksCreate designs1 week3 weeks5 weeksDevelop marketing plan1 week2 weeks4 weeksBuild app2 weeks6 weeks10 weeksTest app1 week2 weeks4 weeksFix bugs1 week2 weeks4 weeksSubmit to app stores1 week2 weeks4 weeksMarket launch2 weeks4 weeks8 weeks

4. Calculate Expected Time

Using the PERT formula:

TaskExpected TimeMarket research4 weeksDefine features2 weeksWrite code8 weeksCreate designs3 weeksDevelop marketing plan2 weeksBuild app6 weeksTest app2 weeksFix bugs2 weeksSubmit to app stores2 weeksMarket launch4 weeks

5. Determine Critical Path

The critical path is the longest sequence of dependent tasks:

Market research (4 weeks) → Define features (2 weeks) → Write code (8 weeks) → Create designs (3 weeks) → Build app (6 weeks) → Test app (2 weeks) → Fix bugs (2 weeks) → Submit to app stores (2 weeks) → Market launch (4 weeks)

Total time = 33 weeks

6. Create PERT Chart

The PERT chart maps out the project plan visually:

[PERT chart image]

7. Optimize Schedule

Potential optimizations:

• Overlap code writing with creating designs

• Add resources to critical coding tasks

• Start app submission and marketing plan in parallel with testing phase

8. Update Chart

As project progresses, update actual start/finish dates, task times, and critical path.

This example demonstrates how to build a PERT chart step-by-step to schedule key tasks, visualize dependencies, and optimize the project timeline.

Benefits of PERT Charts

PERT charts offer many benefits for planning and managing projects:

• Provides overview of entire project from start to finish

• Maps dependencies between tasks

• Estimates task durations including uncertainties

• Identifies critical path to meet deadlines

• Enables resource scheduling and allocation

• Monitors progress to completed tasks vs plan

• Updates easily as plans change

• Identifies schedule risks and bottlenecks

• Facilitates collaboration across teams

• Optimizes timelines to complete projects faster

PERT gives project managers greater oversight into task sequencing, resource usage, and scheduling to improve the efficiency and success of project execution.

PERT vs Gantt Charts

PERT and Gantt charts are two common project management tools used to plan and schedule projects. Though similar, there are some key differences:

PERT ChartsGantt ChartsUsed for complex projects with dependenciesBetter for simpler projectsEmphasizes tasks & dependenciesEmphasizes timelineNetwork diagram layoutBar chart layoutCritical path focusMilestone focusProbabilistic time estimatesFixed time estimatesMore flexible schedulingMore rigid scheduling

In summary:

• PERT is best for complex projects with many interdependent activities.

• Gantt charts work well for projects with defined milestone dates. 

Many project managers use PERT and Gantt charts together. PERT provides task sequencing and dependencies while Gantt charts display fixed schedules and milestones. Together they offer comprehensive project planning and scheduling capabilities.

PERT Chart Templates

There are many PERT chart templates available to help you create PERT charts for your projects. Here are some options:

• Excel PERT chart templates - Create network diagram and analyze critical path

• Word PERT chart templates - Printable PERT charts for hand drawing

• PowerPoint PERT chart templates - Slide with PERT chart example and layouts

• SmartDraw PERT chart template - Visual editor to build professional PERT charts

• Lucidchart PERT chart template - Cloud-based visual collaboration tool

• Free templates online - Download free PERT chart templates

These templates provide starter PERT charts you can customize for your specific project plans. Using a pre-built PERT chart template helps you get started quickly in creating useful project schedules.

PERT Chart Software

There are also many software tools available to help create, manage, and update PERT charts:

• Microsoft Project - Build PERT charts and Gantt charts to schedule projects

• Smartsheet - Online project management with Gantt and PERT charts

• Wrike - Project scheduling tool with interactive PERT charts

• TeamGantt - Web-based project planner with dependencies and GANTT charts

• LiquidPlanner - Project planning with resources, tasks, and dependencies

• OpenProject - Open source collaborative project management

• OmniPlan - Mac desktop app with interactive PERT and Gantt charts

• ConceptDraw - Diagramming and chart visualization software

Project management software makes it easier to develop, update, share, and collaborate on complex PERT chart schedules. Look for tools that integrate both PERT and Gantt chart features for maximum project planning capabilities.

Tips for Using PERT Charts

Here are some top tips for creating effective PERT charts and successfully using them to manage projects:

• Involve team in estimating task times for accuracy

• Break down work into manageable tasks of a few days or weeks 

• Clearly define milestones and deliverables

• Identify all dependencies between tasks

• Set optimistic, pessimistic, and realistic time estimates

• Focus on critical path tasks to prioritize work

• Update PERT chart as project progresses

• Review PERT chart often to communicate status

• Look for opportunities to crash the schedule

• Use software tools for easy creation and updates

• Integrate PERT chart with Gantt chart for schedule

• Make sure chart is easy to read and interpret

Following these tips will help maximize the value of your PERT charts and support effective project planning.

Key Takeaways

• PERT is a project management technique used to schedule tasks with dependencies and determine critical path.

• PERT charts provide a graphical overview of project tasks, timelines, and critical path. 

• Follow key steps to create a PERT chart: list tasks, identify dependencies, estimate times, determine critical path.

• Review PERT charts regularly to monitor project progress and adjust schedules.

• Use PERT chart software and templates to create professional schedules.

• Combine with Gantt charts for comprehensive project planning and tracking.

• PERT enables better project scheduling, control, and resource management.

Mastering PERT methodology using detailed network diagrams provides significant advantages for managing complex projects. Use this guide to start creating and leveraging PERT charts for your next project!