⟩ What is scheduled performance index (SPI)?
This is a measure of schedule efficiency expressed as the ratio of earned value to planned value. An SPI of 1.0 means that the work actually done so far is exactly the same as the work planned to be done so far. When it is greater than 1.0, project is ahead of schedule meaning more work than planned has been completed and when less than 1.0, it is behind schedule.