Which statement correctly describes Schedule Performance Index (SPI)?

Which statement correctly describes Schedule Performance Index (SPI)?

• A. SPI = BCWP ÷ BCWS
• B. SPI = BCWS ÷ BCWP
• C. SPI = ACWP ÷ BCWS
• D. SPI = BCWP ÷ ACWP

Answer: (A)

Schedule Performance Index measures how efficiently the project is progressing against the plan by comparing the value of work actually performed to the value of work that was planned to be performed. The correct expression is the Budgeted Cost of Work Performed divided by the Budgeted Cost of Work Scheduled. In other words, SPI = BCWP ÷ BCWS. This ratio shows schedule health: an SPI of 1 means on schedule, greater than 1 means ahead of schedule, and less than 1 means behind. The other forms would not reflect schedule performance correctly—using BCWS ÷ BCWP inverts the ratio, and using actual cost of work performed blends in cost data, which is what the Cost Performance Index is for rather than the Schedule Performance Index.

Schedule Performance Index measures how efficiently the project is progressing against the plan by comparing the value of work actually performed to the value of work that was planned to be performed. The correct expression is the Budgeted Cost of Work Performed divided by the Budgeted Cost of Work Scheduled. In other words, SPI = BCWP ÷ BCWS.

This ratio shows schedule health: an SPI of 1 means on schedule, greater than 1 means ahead of schedule, and less than 1 means behind. The other forms would not reflect schedule performance correctly—using BCWS ÷ BCWP inverts the ratio, and using actual cost of work performed blends in cost data, which is what the Cost Performance Index is for rather than the Schedule Performance Index.