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Estimating Activity Durations

5 minutes 5 Questions

Estimating Activity Durations is a key process in project time management that involves determining the amount of time required to complete each activity defined in the project scope. Accurate duration estimates are critical for creating a realistic project schedule and ensuring that time constraints are met. Several techniques can be used to estimate activity durations, including: - **Expert Judgment**: Leveraging the experience and insights of individuals or groups with relevant expertise to provide duration estimates based on similar past projects or activities. - **Analogous Estimating**: Using historical data from similar activities in previous projects to estimate durations, which is quicker but less precise. - **Parametric Estimating**: Applying statistical relationships between historical data and other variables (e.g., cost per unit, time per unit) to calculate durations. - **Three-Point Estimating**: Calculating an estimate using three scenarios – optimistic, pessimistic, and most likely durations – and combining them (often using a weighted average) to account for uncertainty. - **Bottom-Up Estimating**: Breaking down activities into smaller, more manageable components and estimating the duration of each, then aggregating them to get the total duration. The estimation process should consider various factors, such as resource availability, skill levels, potential risks, and environmental conditions. Including buffers or contingency reserves may also be prudent to accommodate uncertainties. Accurate activity duration estimates enable the development of a realistic schedule baseline against which project performance can be measured. They also aid in resource planning and budgeting. Regularly reviewing and updating duration estimates as the project progresses can help in adapting to changes and keeping the project on track. In conclusion, Estimating Activity Durations is a fundamental aspect of activity definition and sequencing, providing the necessary information to build an effective schedule that guides project execution and control.

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PMI-SP - Activity Definition and Sequencing Example Questions

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Question 1

You are leading a project with tasks that have been performed regularly in prior projects. You need an estimation method that can provide quick and reasonably accurate results. What technique should you primarily use?

Correct Answer: Analogous Estimating

The most appropriate technique in this situation would be Analogous Estimating, as it's a technique that estimates the cost of project tasks using the actual cost of previous, similar tasks. Considering the fact that the tasks have been performed regularly in prior projects, Analogous Estimating can provide quick and reasonably accurate results. Monte Carlo Analysis, on the other hand, is used for risk analysis and not great for cost estimations. 3-point Estimating requires ample information about the possible variation in the task's performance, which may not always be accessible quickly. Lastly, Parametric Estimating uses statistical modeling and requires a lot of specific data, making it more time-consuming and less suited for quick estimates.

Question 2

You're managing a software development project with a high level of uncertainty. You have been asked to present various scenarios based on different estimates and their probabilities. What technique would you employ?

Correct Answer: Monte Carlo Analysis

The best technique to use in this scenario is Monte Carlo Analysis (id 152750). This technique is designed for risk analysis by creating models of possible results by substituting a range of values, a probability distribution, for any factor that has inherent uncertainty. It then calculates results over and over, each time using a different set of random values from the probability functions. The other techniques mentioned: 3-point Estimating, Analogous Estimating and Parametric Estimating, while useful in their own contexts, do not handle the situation of presenting various scenarios based on different estimates and their probabilities as effectively as Monte Carlo Analysis does. Therefore, they are not the optimal choices in this situation.

Question 3

You are coordinating a construction project. After a careful examination of all the construction tasks, you find two tasks that seem to take a random amount of time each time they are performed. Which method would best suit to estimate these tasks' durations?

Correct Answer: Monte Carlo Simulation

Monte Carlo Simulation is the best method to estimate the duration of construction tasks that seem to take a random amount of time each time they are performed. This is because Monte Carlo Simulation allows you to model the probability of different outcomes in a process where the outcome is uncertain, such as in these tasks. It does this through the use of random variables and iterations, providing a range of possible outcomes and the probabilities that they will occur for any choice of action On the other hand, Analogous Estimating involves using the actual duration of a similar previous task as the basis for estimating the duration of the current task. It wouldn't be as effective in this case because we are dealing with tasks that take a random amount of time each time they're performed Parametric Estimating would also not be the best fit. It relies on statistical relationships between historical data and other variables to calculate an estimate for activity parameters, such as cost, budget, and duration Lastly, Three-Point Estimating relies on multiple estimates (e.g., optimistic, pessimistic, and most likely) to derive an estimate. While it could theorically be used given that you have an idea of the range, the random nature of the task durations makes Monte Carlo Simulation a better estimation method in this case.

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