The correct equation for schedule variance (SV) is earned value:

According to the PMBOK® Guide, Schedule Variance (SV) is a metric used in Earned Value Management (EVM) to determine whether a project is ahead of, on, or behind its baseline schedule.

The Formula: Schedule Variance is mathematically expressed as:

$$SV = EV - PV$$

Where EV is the Earned Value (the measure of work performed expressed in terms of the budget authorized for that work) and PV is the Planned Value (the authorized budget assigned to scheduled work).

Interpreting the Result:

Positive SV ($ > 0$): Indicates the project is ahead of schedule (more work was performed than planned).

Negative SV ($ < 0$): Indicates the project is behind schedule (less work was performed than planned).

Zero SV ($=0$): Indicates the project is exactly on schedule.

Context in Control Costs: SV is a critical indicator in the Control Costs and Control Schedule processes. It provides a more accurate picture of schedule health than simply looking at dates, as it relates the physical work completed to the financial baseline.

Analysis of Other Options:

B. minus actual cost [EV - AC]: This is the formula for Cost Variance (CV). It measures budget performance rather than schedule performance.

C. divided by planned value [EV/PV]: This is the formula for the Schedule Performance Index (SPI). While it also measures schedule efficiency, it is an index (ratio) rather than a variance (difference).

D. divided by actual cost [EV/AC]: This is the formula for the Cost Performance Index (CPI), which measures the cost efficiency of the project.