Schedule Performance Index |
This guideline describes how to use a Schedule Performance Index (SPI) to measure how effectively you are using time.
Main Description
### Overview The Schedule Performance Index (SPI) measures how effectively you are using time in an iteration or in a project. This helps you see the trend of how are you are progressing compared to the plan. You can use SPI for iteration plans or project plans. SPI helps the team to understand the efficiency of spending time and they can adjust future plans based on the trends recorded in previous SPIs. ### Measurement Method SPI = Earned Value / Planned Value Earned Value = Value of completed work items to date in terms of the budget assigned to the work item. This can be the number of earned velocity (hours, days, ideal days, points) to date. Planned Value = Planned value of completed work items to date. This can be planned velocity (hours, days, ideal days, points) to date. ### Measurement Analysis SPI indicates how efficiently the project team is spending the time against the plan. SPI should be as close to one as possible. If SPI is more than one, it indicates a favorable condition, which shows that the team is getting more work done than they expected according to the plan. If the SPI is lower than one, it indicates an unfavorable condition, thus the opposite result. In the following table, by the end of week 4 (9/26/2008), the teams planned to complete 48 hours of work, but they completed only 36 hours of work. Therefore, the SPI to date of this project is 0.75 (36/48). This indicates that for each eight-hour working day, they are doing only six hours of the work that they had planned to do, which means that they are accomplishing only 75% of the planned work each day, on average.
Dates | Plan Value (person-hours) | Earned Value (person-hours)
09/05/2008 | 6 | 6
09/12/2008 | 20 | 20
09/19/2008 | 32 | 32
09/26/2008 | 48 | 36
10/3/2008 | 87 |
© Copyright IBM Corp. 1987, 2009. All Rights Reserved.