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figure10.1to10.5.pdf
Task Predecessor
Homeowner Acquire lawn materials
Remove debris Teens and youth group
Teens 2
1,2 Prepare soil Plont lawn seed
3 3 Teens
Plant shrubs 2 Teens 5
Correct
Finish Start
Network diagram with milestones at the start and finish.
This network has two Concurent paths.
Incorrect
Start Finish
The most common network diagram mistake is removing all concurrent tasks for the same resource. Resource constraints may prevent tasks 4 and 5 from being pertormed at the same time, but that
shouldnt change the network. The network represents only task sequence constraints.
FIGURE Network diagram 10.1 developed from a predecessor table.
Milestones Are Useful Markers
In setting up the sequence of events,
many project managers find it useful
to mark significant events in the life of a project. These markers-called milestones-are often used in work breakdown structures and network diagrams (see Eigure 10.2). Milestones have zern duration, so adding them to
affect the schedule at Back to page i a Tnere are iaree sreat reasons to
Complete salmon data collection.
During an environmental impact study, the project uses data from a federal agency. Task 4.1 will not be able to start until at least July 14, the day the federal report is released.
FIGURE 10.2 Milestones can show external dependencies. Finish-to-start The most common task relationships on the network are finish-to-start. The first task must finish before the next one can start.
MTWT|F |M| T |w T| F
Task A must finish before Task B can start.
Start-to-start The successor task can start as soon as the predecessor task starts. The example shows a painting company, painting all the
rooms on one floor of an office building. After the first room is prepared, both the prep crew and the paint crew can be working at the same time.
Overlapping the tasks reduces the total duration of the project.
MTwT |F |M|T |wlT|E| Prep
Paint B
Task A must start before Task B can start.
Finish-to-finish The successor task can finish only when the prede cessor task is finished. The example shows the last two tasks of a design phase. Planning for the construction phase can begin before the final design approval, but it cannot finish until design is complete.
MTwT| F |M|T|wlT| F Design approval
A
Planning for the next phase B
Task A must finish before Task B can finish.
FIGURE10.3 Task relationships.
CONCEPr PLANNING STEP THREE: STIMATE WORK PACKAGES
In order to determine the cost and duration of an entire project, it's
CONCEP PLANNING STEP THREE: ESTIMATE WORK PACKAGES
In order to determine the cost and duration of an entire project, it's necessary to builda cost and schedule estimate for each work package; this is
called bottom.up estimating. A lot of
information is generated in the estimating process, so it is critical to record it in a systematic manner. (Table 10.1 shows the work package estimates for the home landscape project. Tables 10.2 to 10.5 illustrate some of the variables that affect work package estimates.)
The schedule estimate for a task measures the time from initiation to completion. This estimate is usuallyy referred to as duration of a task. When building a schedule estimate, it's important to include all the time the task will span. For instance, it may take only 1 day to order materials, but if it takes 10 days for delivery, the total duration of the task will be 11 days. Similarly, while a certain decision might take only 2 hours to make, it might be more realistic to estimate duration at 5 days if the decision maker is likely to be busy at that time.
Cost estimates come from four sources:
1. Labor estimates. These project how much human effort will be put into a task. If three people work 8 hours a day for 3 days, the total labor estimate will be 72 hours. On
11.
10.1 Home Landscape TABLE Project Work Package Estimates
ID Task Name
Duration Labor Resource Hours Names
Design home
5 days 80 hrs.
1 Homeovwner [0.5], Teens [1.5 landscape
2 Put in lawn
3 Acquire 2 days lawn
64 Homeowner, hrs. Teens [3]1
materials
Install sprinkler system
4
5 Identify 1 day sprinkler locationns
Fixed Contractor, fee,8 Homeowner hrs.
Dig trenches
6 2 days Fixed Contractor fee
7 Install pipe and hardware
3 days Fixed Contractor fee
1 day 8 Cover sprinkler system
Fixed Contractor fee
9 Plant grass
10 Remove 4 days debris
Teens [31, Youth Group
256 hrs.
Teens [3] Rototiller
4 days 11 Prepare soil
12 Plant lawn seed
96
hrs.
1 day 16 Teens [2] hrs.
1 day 12 Plant lawn seed
16 Teens [2] hrs.
13 Plant shrubs
14 Build fence
6 days 96 Teens [2] hrs.
15 Acquire 2 days 16 Homeowner fence hrs. material
16 Install fence
1 day 17 Mark fence line
32 Homeowner, hrs. Teens [3]
5 days 18 Install posts
80 Teens (21 hrs.
6 days Teens [3]1 19 Install |fencing and gates
144 hrs.
20 Paint/stain |3 days fence and
gates
72 Teens [31 hrs.
On task 1, both the homeowner and the teens are working 4 hours per day.
Fixed.price bids. Fixed.estimate
costs can replace the three
previous cost sources. For example, a vendor or subcontractor might make a fixed.
price bid that includes labor, equipment, and materials. Fixed.
price bids mean that the vendor takes responsibility for costs; should there be overruns, the cost to the project will not change. (The landscape project in Table 10.1
1.
TABLE 10.2 Work Package Estimate: Example 1
Task description: During an environmental study, a power
company counts salmon during a 40-
day salmon run.
Assumption: The federal agency Overseeing the power company dictates the length of the study.
Materials: None
Duration: 40 days
Labor and Equipment Table
Type Average Use
Total
1@ 10 hrs./day
Salmon 400 hrs. specialist
2@ 10 hrs./day
800 hrs. Field technician Truck 1 all day 40 days |Increasing the number of people on this task does not change the duration but it could increase the accuracy of
the study. Is it really necessary to concentrate on costs when trying to build a realistic schedule? It is, because each cost represents a resource constraint. Costs such as hiring subcontractors and purchasing materials will constrain the schedule. Later on, the schedule will be adjusted to account for these resource constraints (this is the fifth step of planning), but before adjusting the schedule we need to identify all the resource requirements, one work
package at a time.
TABLE 10.3 Work Package Estimates: Example 2
Task description: During a training project, software is upgraded on 20 workstations in a training room.
Assumption: The average time to install the software is 2 hours per workstation. Testing is 1 hour per workstation. Only one person can work on one workstation at a time.
First Estimate
Duration:5 days
Materials: 20 copies of the new software
Labor and Equipment Table
Type Average Total Use
40 hrs. Computer technician
1@8 hrs./day
Tester (user or 1@4 technician)
20 hrs. hrs./day
Software test
kit 1 per tester 1 test
kit The training manager does not want the training room out of use for a whole week. In fact, he wants the upgrade done overa weekend so the training room doesn't lose any
availability. Revised Estimate
Duration: 2 days
Materials: 20 copies of the new software
Labor and Equipment Table
Type Average Total Use
Computer 2@ 10 40 hrs.
How Productivity Relates to Duration
When estimating the number of people needed for a task, you will need to consider their productivity. Adding people to simple tasks always reduces the duration. Productivity is said to be constant when the total labor hours do not change as the number of people assigned to the task changes. (The productivity of the technicians in Table 10.3 was constant, and so was the "Remove debris" task in Table 10.1)
However, in the case of tasks involving knowledge workers, adding more workers does not always result in greater productivity and shorter duration for a task. For example, if two engineers are working ona complex problem, adding three more may actually slow the task and produce no recognizable change in product quality. The result is a measurable decrease in productivity because the cost for labor increases while the product stays the same. (The first revised estimate in Table 10.5 is another example of this factor.)
TABLE 10.4 Work Package Estimates: Example 3
Task description: A government agency is mapping a forest. Aerial photography of the entire area is the first step in creating the maps.
Assumption: An aerial photography subcontractor rents airplanes
(complete with pilots and photographers). The agency has one Scientist ride with every airplane. Thhe
TABLE 10.4 Work Package Estimates: Example 3
Task description: A government agency is mapping a forest. Aerial
photography of the entire area is the first step in creating the maps.
Assumption: An aerial photography subcontractor rents airplanes
(complete with pilots and photographers). The agency has one Scientist ride with every airplane. The forest is broken into 60 squares. They can photograph one square per day. During the flight, a ground technician stays in radio contact with the scientist to answer mapping questions. First Estimate
Duration: 60 days Materials: None
Labor and Equipment Table
Type Average Total Use
1@8 |hrs./day
Scientist (in 480 hrs. plane)
480 hrs. 1@8 hrs./day
Airplane
480 hrs. 1@8 hrs./day
Ground
technician The forest area traditionally has so much cloudy weather that the agency estimates there will be only one clear
day out of every three, but the photography needs to take place
during the three months of summer
when there is no snow.
TABLE 10.5 Work Package Estimates: Example 4
Task description: A systems analyst is working on three projects at the same time. One of her project managers asks her to estimate the design of aa
subsystem. Assumption: She will continue to work on all three projects simultaneously. First Estimate
Duration: 40
days Materials: None
Labor and Equipment Table
Type Systems analyst
Total Average Use
1@ 2.5 hrs./day
100
Her project manager needs the design performed much faster and suggests he could get another analyst to work with her part.time.
Revised Estimate
Duration: 30 days
Materials: None
Labor and Equipment Table
Average Use Total
2@ 2.5 hrs./day
Type Systems analyst
150
Adding people to a design task can speed up some of the work, but much of it will be done together so it results in an increase in the total labor cost. It is possible the resulting design will be better, but that is another
assumption.
be better, but that is another assumption. Then the project manager asks her what it would take to get it done the fastest. She responds, "Talk to my other project managers and arrange to get me completely off those projects for a few weeks so I can concentrate 100 percent on yours."
Revised Estimate
Duration: 10
days Materials: None
Labor and Equipment Table
Type Average Use Total 1@ 8 hrs./dayy
80 Systems analyst Not only is she able to spend more time per day on this task but she knows that if she is able to concentrate on it 100 percent she will be more productive.
Another point to consider when measuring productivity is that people who spend all their time on one project are usually more productive than people who spread their time across multiple projects (again, see Table 10.5). The analyst estimates that the most productive way for her to work- requiring the fewest hours and fewest days-is to be able to devote 100 percent of her attention to one project.
When calculating hours for your part.
time project workers, it is usually unnecessary to figure out exactly what hour of which day they'll be working on your project. By assigning a
unnecessary to figure out exactly what hour of which day they'll be working on your project. By assigning a resource.level assumption, such as
"two hours per day," to all their tasks, you proportionally increase the estimates for the duration of the task. This approach allows each individual team member to decide for himself or herself when to actually work on the task. It doesn't matter whether they get started on it as soon as it's scheduled or work on it the last day. All you need to do to prepare a detailed plan is to
give them a start time anda completion time.
As you can see, there is much to be considered when estimating the costs and duration of work packages. Chapter 12 discusses the subject further, with many more tips and
techniques.
PLANNING STEP FOUR: CALCULATE AN INITIAL SCHEDULE
Calculating a schedule may be one of the most well known, but unappreciated, of all project management techniques. It can be
particularly tedious and time.
consuming when done by hand for large projects. Yet it is the key to establishing realistic schedules and meeting them. (The tedium involved is a compelling reason to use project
management software.) Ac dicco onrlior tho initinl
