Supply Chain management Chapter 3

Flashcard maker : Lily Taylor
A simple CPM network has five activities, A, B, C, D, and E. A is an immediate predecessor of C and of D. B is also an immediate predecessor of C and of D. C and D are both immediate predecessors of E. Given the above scenario, which of the following is correct?
There are four paths in this network.
Which of these statements regarding time-cost tradeoffs in CPM networks is true?
Crashing shortens the project duration by assigning more resources to one or more of the critical tasks.
With respect to PERT and CPM, slack__________
is the amount of time a task may be delayed without changing the overall project completion time.
The critical path for the network activities shown below is _______ with duration _______.

Activity

Duration
Immediate Predecessors
A
4

B
2
A
C
7

D
4
A
E
5
B,C,D

A-D-E; 13
The three phases involved in the management of large projects are:
Planning, scheduling, and controlling
An activity on a PERT network has these time estimates: optimistic = 1, most likely = 2, and pessimistic = 5. Its expected time is:
2.33
The critical path of a network is the__________
longest time path through the network.
Dummy activities__________
are used when two activities have identical starting and ending events.
The true statement is that crashing shortens the project duration by assigning more resources to one or more of the critical tasks in a project. Any activity can be crashed if the duration of time can be reduced by adding resources (additional labor, materials, etc.); if the amount of time won’t be reduced there is no need to crash a project. Crashing projects can occur with single (or multiple) critical paths.
With respect to PERT and CPM, slack is the amount of time a task may be delayed without changing the overall project completion time.
Latest start is the term used to describe the latest time an activity can be started without delaying the entire project. Latest finish is the term used to describe the latest time an activity can be completed and not delay the completion time of the entire project.
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Which of the following is a basic assumption of PERT?
No activity in the network must be repeated.
The critical path for the network activities shown below is A-D-E with duration 13. Critical path activities are those activities that will delay the entire project if they are not completed on time. In this case, activity A is an immediate predecessor for A and D and the final activity is E. The sum of the duration for this network is 13 (4+4+5 = 13).
2.33
The three phases involved in the management of large projects are planning, scheduling, and controlling. The planning phase involves defining the scope of the project, setting goals, and organizing the team. The scheduling phase involves aligning resources (people, money, supplies) for specific activities. The controlling phase involves monitoring the use of resources and adjusting goals and timelines to meet time and cost specifications.
Expected time (t) is calculated using the following formula: t = (a + 4m + b)/6, where
a = optimistic time estimate (in this case 1); m = most likely time estimate (in this case 2); and b = pessimistic time estimate (in this case 5). Therefore;
An activity on a PERT network has these time estimates: optimistic = 1, most likely = 2, and pessimistic = 5. Its expected time is:
t = (1 + 4*2 + 5)/6
t = 14/6
t = 2.33
An activity has an optimistic time of 15 days, a most likely time of 18 days, and a pessimistic time of 27 days. What is the expected time?
19 days
Which of the following is determined during the forward pass?
Early start
An activity on a PERT network has these time estimates: optimistic = 2, most likely = 5, and pessimistic = 10. Its expected time is:
5.33
An activity on a PERT network has these time estimates: optimistic =2, most likely = 3, and pessimistic 8. Its expected time and variance (if it is a critical activity) are:
3.67 and 1
Which of the following statements regarding PERT analysis is true?
Only critical activities contribute to the project variances.
PERT analysis computes the variance of the total project completion time as:
The sum of all variances of all activities on the critical path
PERT analysis assumes that no activity in the network must be repeated. PERT assumes that critical and non-critical path activities must be completed. CPM assumes that activity times are known with certainty.
Expected time (t) is calculated using the following formula: t = (a + 4m + b) / 6, where
a = optimistic time estimate (in this case 2); m = most likely time estimate (in this case 3); and b = pessimistic time estimate (in this case 8). Therefore;

t = (2 + 4*3 + 8) / 6
t = 22 / 6
t = 3.67

Variance (v) is calculated using the following formula: v = [(b-a) / 6]2, where b= pessimistic time estimate (in this case 8) and a = optimistic time estimate (in this case 2). Therefore;

v = [(b-a) / 6]2
v = [(8-2) / 6]2
v = [6/6]2
v = [1]2
v = 1

Which of these statements regarding time-cost tradeoffs in CPM networks is true?
Crashing shortens the project duration by assigning more resources to one or more of the critical tasks.
Which of the following statements regarding Gantt charts is true?
Gantt charts are visual devices that show the duration of activities in a project.
__________ is the amount of time an individual activity in a network can be delayed without delaying the entire project.
Slack time
The critical path for the network activities shown below is _______ with duration _______.

Activity
Duration
Immediate Predecessors
A
2

B
4

C
6
A,B
D
1
A,B
E
2
B,C,D

B-C-E; 12
A project’s critical path is composed of activities A (variance .33), B (variance .67), C (variance .33), and D (variance .17). What is the standard deviation on the critical path?
1.22
An activity has an optimistic time of 11 days, a most likely time of 15 days, and a pessimistic time of 23 days. What is its variance?
4
The true statement is that gantt charts are visual devices that show the duration of activities in a project.
Gantt charts are not a precedence diagraming activity or method (such as AON or AOA networks) that create timelines and present the sequence in which activities should be performed. Instead, Gantt charts graphically specify all of the tasks involved in a project and how much time should be spent doing each activity. The four standard spines of Methods, Materials, Manpower, and Machinery are part of cause and effect diagrams and are typically used in the quality control process.
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The standard deviation on the critical path is 1.22. To calculate the standard deviation you take the square root (?) of the sum of the critical path activity variances. In this case,
Standard deviation = ?.33+.67+.33+.17
Standard deviation = ?1.5
Standard deviation = 1.22
The variance for this activity is 4. Variance (v) is calculated by using the following formula: v = [(b-a) / 6]2, where b = pessimistic time estimate (in this case 23) and a = optimistic time estimate (in this case 11). Therefore:
v = [(b-a) / 6]2
v = [(23-11) / 6]2
v = [12 / 6]2
v = [2]2
v = 4
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In a PERT network, non-critical activities that have little slack need to be monitored closely__________
because near-critical paths could become critical paths with small delays in these activities
WBS stands for which of the following project management tools?
Work Breakdown Structure
The Beta distribution is used in project management to
Calculate expected activity times
The Beta distribution is used in project management to calculate expected activity times. The beta distribution is used to calculate expected activity times by weighting three time estimates including the optimistic time of an activity, the pessimistic time of an activity, and the most likely time for an activity.
The EF of an activity is the:
ES + Activity time

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