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PMP Practice: Apply Intervention Strategies

Question 2 of 5 in Remove Impediments and Manage Issues

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Shota Hayashi is managing a legacy system migration project for Turbulent Otter Games. The project involves upgrading warehouse management software across 12 distribution centers. During the planning phase, the team identified a critical impediment: a key vendor module required for real-time inventory tracking may not be available on time. The vendor has provided three possible delivery scenarios: - Best case: Module ready in 3 weeks (25% probability) - Most likely: Module ready in 5 weeks (50% probability) - Worst case: Module ready in 9 weeks (25% probability) The project's critical path includes this module integration, and any delay directly impacts the project completion date. Kayla needs to calculate the expected delivery time to update the project schedule and communicate realistic expectations to the executive steering committee, who have already expressed concern about delays affecting Q4 revenue targets. Based on the three-point estimate, what is the expected delivery time for the vendor module that Kayla should use for schedule planning?
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Correct answer: 5.5 weeks

Explanation

The expected delivery time is calculated using the weighted average formula for three-point estimates with discrete probabilities. Since specific probability percentages are provided (25%, 50%, 25%), we multiply each scenario by its probability and sum the results: (3 weeks × 0.25) + (5 weeks × 0.50) + (9 weeks × 0.25) = 0.75 + 2.50 + 2.25 = 5.5 weeks. This expected value approach provides Kayla with the most statistically sound estimate for schedule planning. By calculating and communicating this realistic timeframe to the steering committee, she addresses their concerns proactively and manages expectations appropriately. This calculation becomes the basis for determining whether contingency reserves are adequate and whether the impediment requires additional risk response actions such as identifying alternative vendors or adjusting the project timeline.

**Why not B:** The 6.0-week estimate would result from a simple average of the three scenarios: (3 + 5 + 9) ÷ 3 = 5.67, which rounds closer to 6.0—but a simple average treats all scenarios as equally probable. The given probabilities are 25%, 50%, and 25%, meaning the most likely scenario (5 weeks) should receive double the weight of the best and worst cases, making the probability-weighted calculation the statistically appropriate approach.

**Why not C:** The 5.0-week estimate represents only the most likely scenario (50% probability) and ignores the weighted contributions of the best-case and worst-case scenarios. Using the most likely case alone does not account for the full range of uncertainty and understates the expected delivery time, which could lead to an optimistic schedule commitment that fails to materialize when actual delivery skews toward the 9-week scenario.

**Why not D:** The 5.7-week estimate does not correspond to any standard three-point estimation formula applied to these inputs. The PERT beta distribution formula (O + 4M + P) ÷ 6 = (3 + 20 + 9) ÷ 6 = 5.33 weeks, and the probability-weighted calculation yields 5.5 weeks. A result of 5.7 weeks may arise from a calculation error or an incorrect weighting assumption and does not reflect the discrete probabilities specified in the scenario.

Key Concept

This question covers Apply Intervention Strategies under Remove Impediments and Manage Issues (Business Environment).

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