PERT CPM- Operations Research Quiz

2.

Given, expected duration of the project = 47 days, variance = 9 days. Expected Time for Project Completion: 50 days Z : 0.33 1.0Area : 0.1293 0.3413 What is the probability of completing the project within three days, more or less than the expected time?

0.5000
0.6826
0.2586
0.3174

Correct Answer

A. 0.6826

Explanation

The answer is 0.6826 because the expected duration of the project is 47 days with a variance of 9 days. The expected time for project completion is 50 days. By using the Z-score formula, we can calculate the probability of completing the project within three days of the expected time. The Z-score for three days is (3 - 50) / √9 = -47 / 3 = -15.67. Looking up this Z-score in the Z-table, we find that the corresponding probability is 0.6826. Therefore, there is a 68.26% chance of completing the project within three days, more or less than the expected time.

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3.

Which of these is not correct

PERT is probabilistic in nature.
CPM is deterministic in nature.
CPM is event-oriented.
CPM and PERT use similar terminology but were developed independently.

Correct Answer

A. CPM is event-oriented.

Explanation

The given answer states that CPM is event-oriented. This means that CPM focuses on identifying and sequencing specific events or activities that need to occur in a project. CPM does not consider the probabilistic nature of activities and does not involve calculating the expected time or probability of completion for each activity. Instead, it focuses on determining the critical path, which is the sequence of activities that takes the longest time to complete and determines the overall project duration. Therefore, the statement that CPM is event-oriented is correct.

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4.

_________ is not a rule of network construction.

Only one arrow defines each activity.
A network must have only an initial and only one terminal node.
Final nodes and identical initial can identify two activities.
None

Correct Answer

A. Final nodes and identical initial can identify two activities.

Explanation

The rule of network construction states that only one arrow should define each activity. This means that each activity should have a clear and unambiguous starting and ending point. The statement "Final nodes and identical initial can identify two activities" contradicts this rule, as it suggests that multiple activities can be identified by the same starting or ending point. Therefore, this statement is not a rule of network construction.

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5.

Mark the incorrect statement:

A project can be called a set of activities that can be performed in a particular logical sequence.
An activity cannot be represented by more than one arrow, but an arrow can represent one or more activities.
An arrow which is representing an activity may have any kind of length and shape.
All are correct

Correct Answer

A. An activity cannot be represented by more than one arrow, but an arrow can represent one or more activities.

Explanation

The given answer is incorrect because it states that an activity cannot be represented by more than one arrow. In reality, an activity can be represented by multiple arrows, but an arrow can only represent one activity.

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1

6.

It is known that in a project, activity 4-6 has a duration of six days and a total float of three days. The E and L times at node 4 are 8 and 11, respectively, while, at node 6, both are equal to 17.Which of the following is not a true statement about 4-6?

Its free float is three days.
Its independent float is 0.
It is a critical activity.
The ES of this activity is 8.

Correct Answer

A. It is a critical activity.

Explanation

The given answer states that "It is a critical activity" is not a true statement about activity 4-6. This means that activity 4-6 is not a critical activity. A critical activity is one that has zero float, meaning any delay in its completion will cause a delay in the overall project. Since the activity 4-6 has a total float of three days, it means that it can be delayed by up to three days without affecting the project's overall timeline. Therefore, it is not a critical activity.

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7.

Point out which of these is not required in Precedence relationships.

All the predecessor(s) of an activity should be focused on.
Should only focus on immediate predecessor(s).
Should drop redundant predecessors.
All of these

Correct Answer

A. All the predecessor(s) of an activity should be focused on.

Explanation

The correct answer is "All of these." This means that all the options mentioned in the question are not required in Precedence relationships. The question is asking which option is not necessary when considering the predecessors of an activity. The correct answer implies that it is not necessary to focus on all the predecessors of an activity, but rather only the immediate ones. Additionally, any redundant predecessors should be dropped, meaning they are not required to be considered in the Precedence relationships.

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2

8.

Pick the wrong relationship:

Interfering float = Total float – Free float
Total float =Free float + Independent float
Total float ≥ Free float ≥ Independent float
Free float = Total float – Head event slack

Correct Answer

A. Interfering float = Total float – Free float

Explanation

The given relationship "Interfering float = Total float – Free float" is incorrect. Interfering float refers to the amount of float that affects the project's critical path, while total float represents the total amount of time a task can be delayed without delaying the project. Free float, on the other hand, refers to the amount of time a task can be delayed without delaying the start of any successor tasks. Therefore, the correct relationship should be "Interfering float = Total float + Free float".

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9.

Given, expected duration of the project = 47 days, variance = 9 days. What is the probability of not completing the project in 50 days? Z : 0.33 1.0Area : 0.1293 0.3413

0.6293
0.8413
0.1587
0.3707

Correct Answer

A. 0.1587

Explanation

The answer of 0.1587 represents the probability of not completing the project in 50 days. This probability is calculated using the Z-score and the standard normal distribution table. The Z-score is calculated by taking the difference between the expected duration of the project (47 days) and the given duration (50 days), and dividing it by the square root of the variance (9 days). The Z-score of 0.33 corresponds to an area of 0.1293 in the standard normal distribution table. Since the probability of not completing the project in 50 days is the area to the left of the Z-score, the answer is 0.1587.

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1

10.

________ is not true about crashing?

Always pay attention to the critical path and select between critical activities only.
Crashing cost per day = (Crash cost – Normal cost) / (Normal time – Crash time).
Always choose the activity with the least crashing cost.
All are true

Correct Answer

A. Always choose the activity with the least crashing cost.

Explanation

The statement "Always choose the activity with the least crashing cost" is not true about crashing. While it may seem intuitive to choose the activity with the least crashing cost, it is not always the most effective strategy. The decision of which activity to crash should be based on a variety of factors, such as the impact on the critical path, the time saved, and the cost involved. It is important to carefully analyze these factors and make a strategic decision rather than simply choosing the activity with the lowest crashing cost.

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PERT CPM- Operations Research Quiz

CPM is:

Quiz Preview

Given, expected duration of the project = 47 days, variance = 9 days. Expected Time for Project Completion: 50 days Z : 0.33 1.0Area : 0.1293 0.3413 What is the probability of completing the project within three days, more or less than the expected time?

Which of these is not correct

_________ is not a rule of network construction.

Mark the incorrect statement:

It is known that in a project, activity 4-6 has a duration of six days and a total float of three days. The E and L times at node 4 are 8 and 11, respectively, while, at node 6, both are equal to 17.Which of the following is not a true statement about 4-6?

Point out which of these is not required in Precedence relationships.

Pick the wrong relationship:

Given, expected duration of the project = 47 days, variance = 9 days. What is the probability of not completing the project in 50 days? Z : 0.33 1.0Area : 0.1293 0.3413

________ is not true about crashing?