Estimating Activity Durations

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Estimating Activity Durations

• Farrokh Alemi, Ph.D.

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Purpose

• Accuracy matters

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Implicit Assumptions Revealed

• More people, less time

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Source of Data

• Expert opinions
• Time studies
• Statistical analysis

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Source of Data

• Expert opinions
• Time studies
• Statistical analysis

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Source of Data

• Expert opinions
• Time studies
• Stop motion studies
• Diary
• Statistical analysis

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Source of Data

• Expert opinions
• Time studies
• Statistical analysis

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Assessing Experts Opinions

• Assumptions
• Estimate, talk and estimate
• Delphi

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Assessing Experts Opinions

• Assumptions
• Estimate, talk and estimate
• Delphi

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Assessing Experts Opinions

• Assumptions
• Estimate, talk and estimate
• Delphi

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Example of Estimate Talk Estimate
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Example of Estimate Talk Estimate
Thanks for agreeing to help usplease write down
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Example of Estimate Talk Estimate
Responses from different expert are collected and
displayed on the flip chart without attribution
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Example of Estimate Talk Estimate
This is great. Lets discuss why it could take a
long time
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Example of Estimate Talk Estimate
Well it depends on the experience of the person
configuring the system
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Example of Estimate Talk Estimate
And it also depends on how cooperative the
clinicians are.
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Example of Estimate Talk Estimate
Discussion of Assumptions
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Example of Estimate Talk Estimate
You have said please re-estimate
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PERT

• Optimistic
• Realistic
• Pessimistic

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PERT

• Optimistic
• Realistic
• Pessimistic

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PERT Dialogue
How long do you think it would take to send 100
surveys out?
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PERT Dialogue
It all depends. I have seen people do it in 6
hours and I have seen others do it in 1 hour.
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PERT Dialogue
But given what I know about your operations I
think it will take 2 hours.
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PERT Dialogue
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Take Home Lesson

• Estimate-Talk-Estimate and PERT method can
  increase accuracy of estimate of duration of
  activities