# Chapter 5 Estimating Duration, Resource Requirements, and Cost

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Chapter 5 Estimating Duration, Resource
Requirements, and Cost

Dr. Anwar Abu-Zarifa . Islamic University of Gaza . Department of Mechanical & Industrial Engineering © 2017/2018

1

Estimating Duration
Duration is the elapsed time in business working days, not including weekends, holidays, or other nonworking days. Work effort is labor required to complete an activity
Can be consecutive or nonconsecutive hours

Dr. Anwar Abu-Zarifa . Islamic University of Gaza . Department of Mechanical & Industrial Engineering © 2017/2018

2

Variation in Activity Duration
Several causes of variation in the actual activity duration:
Varying skill levels Will be both a help and a hindrance to PM
Unexpected events Example: incorrect shipments of materials
Efficiency of work time  Mistakes and misunderstandings Common cause variation

Dr. Anwar Abu-Zarifa . Islamic University of Gaza . Department of Mechanical & Industrial Engineering © 2017/2018

3

Elapsed time versus work time

Dr. Anwar Abu-Zarifa . Islamic University of Gaza . Department of Mechanical & Industrial Engineering © 2017/2018

4

There are six techniques for initial planning estimates
1. Similarity to other activities  Extrapolate based on recollections of similar activities
2. Historical data  Based on project notebook records of estimated and actual duration  Can be sophisticated database search with regression
3. Expert advice  Vendors may prove good source
4. Delphi technique 5. Three-point technique 6. Wide-band Delphi technique

Dr. Anwar Abu-Zarifa . Islamic University of Gaza . Department of Mechanical & Industrial Engineering © 2017/2018

5

cont.
Delphi technique
Can produce good estimates in the absence of expert advice Extracts and summarizes the knowledge of the group to arrive at an estimate. Each individual in the group is asked to make his or her best guess of the activity duration. Results are tabulated and presented in a histogram labeled First Pass. Those whose estimates fall in the outer quartiles are asked to share the reason for their guess. Group is asked to guess again. Repeat for Second and Third Passes. Average of the third guess is used as the group’s estimate.

Dr. Anwar Abu-Zarifa . Islamic University of Gaza . Department of Mechanical & Industrial Engineering © 2017/2018

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Delphi technique cont.

Dr. Anwar Abu-Zarifa . Islamic University of Gaza . Department of Mechanical & Industrial Engineering © 2017/2018

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Methods for Estimating Task Duration cont.
Three-point technique
Need three estimates of activity duration: Optimistic
The shortest duration one might expect to experience given that everything happens as expected Pessimistic The duration that would be experienced if everything that could go wrong did go wrong, yet the activity was completed Most likely The time usually experienced

Dr. Anwar Abu-Zarifa . Islamic University of Gaza . Department of Mechanical & Industrial Engineering © 2017/2018

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Methods for Estimating Task Duration cont.
Three-point technique

Dr. Anwar Abu-Zarifa . Islamic University of Gaza . Department of Mechanical & Industrial Engineering © 2017/2018

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Methods for Estimating Task Duration cont.
Wide-band Delphi technique
Combines Delphi and Three-Point methods In place of a single estimate, the panel members are asked, at each iteration, to give their O, P, and M estimates for the duration of the chosen task. The results are compiled, and any extreme estimates are removed. Averages are computed for each of the three estimates

Dr. Anwar Abu-Zarifa . Islamic University of Gaza . Department of Mechanical & Industrial Engineering © 2017/2018

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