A project manager discovers that the project is 10% over budget at the halfway point. Which metric shows this?

Correct answer: Cost Performance Index (CPI)

Option D is correct because the Cost Performance Index (CPI) measures cost efficiency as the ratio of Earned Value (EV) to Actual Cost (AC); a CPI below 1.0 indicates the project is over budget, and discovering the project is 10% over budget at the halfway point is precisely what a CPI of approximately 0.91 would reveal. Option A, Variance at Completion (VAC), projects the expected budget surplus or deficit at project completion but does not describe the current performance ratio that reveals a 10% over-budget condition. Option B, Schedule Performance Index (SPI), measures schedule efficiency as the ratio of EV to Planned Value (PV) and indicates whether the project is ahead or behind schedule, not whether it is over budget. Option C, Estimate at Completion (EAC), is a forecast of total project cost at completion; while it uses CPI in its calculation, the EAC itself is a projected dollar figure, not the metric that directly shows the 10% over-budget performance ratio.