SV (Schedule Variance) and SPI (Schedule Performance Index)

1. Schedule Variance (SV):

• Definition: Measures the deviation of the project’s progress from the planned schedule in terms of monetary value or work units.
• Formula: SV=EV?PV

Where:

EV (Earned Value): The value of work actually completed.

PV (Planned Value): The value of work planned to be completed by a specific time.

• Interpretation:

1. Positive SV: Ahead of schedule (more work completed than planned).
2. Negative SV: Behind schedule (less work completed than planned).
3. Zero SV: On schedule.

2. Schedule Performance Index (SPI):

• Definition: A ratio that indicates the efficiency of time utilization in the project.
• Formula: SPI=EV/PV

Where:

EV (Earned Value): The value of work actually completed.

PV (Planned Value): The value of work planned to be completed by a specific time.

• Interpretation:

1. SPI > 1: Ahead of schedule (efficient use of time).
2. SPI < 1: Behind schedule (inefficient use of time).
3. SPI = 1: On schedule (time is utilized as planned).

Example:

Suppose a construction project has the following data:

• Planned Value (PV): $100,000
• Earned Value (EV): $90,000

Calculations:

• SV: SV=EV?PV=90,000?100,000=?10,000
• SPI: SPI=EV/PV=90,000/100,000=0.9

Interpretation:

• SV (-10,000): The project is behind schedule by $10,000 worth of work.
• SPI (0.9): The project is progressing at 90% of the planned rate, indicating inefficiency in time use.