Estimate Activites Duration

This article contains most of the important information you need to know about Estimate Activity durations process in order to answer questions related to this topic in the PMP Exam, I recommend you review this type of articles 1 week before your exam date, all information mentioned are based on PMBOK Guide 6th edition and PMP Exam Prep 9th edition for Rita Maclhy’s, ITTO refers to Inputs, Tools & Techniques and outputs.

This process is a part of Planning Process group and Time Management Knowledge Area with the following ITTO’s


  1. Project Management Plan (Schedule management plan & Scope baseline )
  2. Project Documents ( Activity resources requirements ,Activity List ,Activity Attributes ,Resources breakdown structure , Risk Register , Scope of statement , Resources Calendar , Lessons learned register . , project team assignments , resources requirements )
  3. Organization process assets
  4. Enterprise environmental factors

Tools & Techniques:

  1. Expert Judgment
  2. Analogues estimating
  3. Parametric estimating
  4. Three points estimating
  5. One point estimating
  6. Data Analysis ( Reserve Analysis , Alternative analysis )
  7. Decision making
  8. Meetings



  1. Activity duration estimates
  2. Basis of estimates
  3. Project Document Updates ( activity attributes , assumption log, lessons learned register )


  • It is the time to estimate how much time each activity will take , usually estimators should be those who will do the work or who are almost familiar with the work needs to be done.
  • Padding is a sign of poor project management.
  • There is different estimating techniques :
  1. One-Point Estimating, the estimator submits one estimate per activity , it can be based on expert judgment or historical information or it could be just a guess , It is not used frequently and have a lot of negative effects such as ; it forces padding , it can result in schedule that nobody believes in.
  2. Analogous Estimating (Top-Down ) , It uses expert judgment and historical information to predict the future , it can be done at the project level and can be applied on activity level. The level of accuracy depends on how closely the project or activity matches the past history, it is mainly used when the project is chartered.
  3. Parametric Estimating , looks at relationship between variables on an activity to calculate time or cost estimates , the data can come from historical records from previous projects , industry requirements , standard metrics , it comes like time per code , time per linear meter , time per installation and there is 2 ways of parametric estimating
  4. Regression Analysis, a diagram tracks two variables to see if they are related and creates a mathematical formula.
  5. Learning Curve, The 50th room block work will take less than the first room because of improved efficiency.
  6. Three-Point Estimating, In this method estimators give an optimistic (O), pessimistic (P), and most likely (M) estimate for each activity. It allows more consideration and uncertainty of estimating , three point estimating calculate a risk based expected duration estimate by taking either a simple average or a weighted average of three estimates with the following formula
  7. Triangle Distribution (Simple Average), P+M+O / 3 , It gives equal weight to each of the three point estimates calculating the expected activity duration or cost.
  8. Beta Distribution (Weighted Average) , P+4M+O/6 . It gives stronger consideration for the most likely estimate, this method gives benefits of risk management in reducing the uncertainty of estimates.
  • Beta Expected Activity Duration ( EAD ) +/- SD , where SD is the standard deviation ( P-O)/6 . the start of range is EAD-SD and the end of the range is EAD+SD
  • Heuristics: Generally accepted rule, a best practice or rule of thumb.
  • Accuracy: The conformance to target value.
  • Group decision making is used within the tools in estimating, they will do brainstorming, nominal group techniques and Delphi technique.
  • Reserve analysis. there can be two types of reserves added to the project schedule ,
  1. Contingency Reserves, It is for the identified schedule risks remaining after the plan risk responses process , they are included in the project schedule baseline .
  2. Management Reserves. Additional funds set aside to cover unforeseen risks that would impact the project ability to meet the schedule , management time reserves are not part of project schedule baseline.

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