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How to Read Gantt Chart Variances

A Gantt chart is used in project management to track tasks start and completion dates, ensuring the project is completed on time. Individual project tasks completed too late delay project completion and impact scheduling of succeeding steps, while tasks completed too early may also cause problems as materials may not yet be ready for the next task in the sequence. The difference between scheduled start and end dates and actual start and end dates for the project is called variance. Examining variance helps the project manager complete the project on time.

Instructions

- 1
  Understand the Gantt chart table. The table has six columns: Baseline Start, Baseline Finish, Actual Start, Actual Finish, Start Variance and Finish Variance. Baseline start and finish dates are agreed upon by the project sponsor and manager. Baseline start and finish data are agreed upon for each individual task as well as the overall project. Actual start and finish dates are when the work for each task and the overall project was actually started and completed. Variance is the difference between actual start and finish dates compared to baseline dates.
- 2
  Interpret negative chart variance. Chart variance refers to the difference between baseline and actual task start dates. Negative chart variance means tasks were started early. An example would be a project task with a baseline start date of Thursday April 14, 2011 that started Monday April 11; the negative chart variance is three days.
- 3
  Examine positive chart variance. If the actual start date is later than the baseline start date, chart variance is positive. For example, if the baseline start date was Thursday April 14 and it did not start until Monday April 18, the positive chart variance would be two days, because chart variance is excludes weekends.
- 4
  Interpret negative finish variance. Finish variance refers to the difference between baseline and actual finish dates. If the actual finish date is early, finish variance is negative. Subsequent tasks will have to be started earlier as a result.
- 5
  Interpret positive finish variance. If the actual end date is late, finish variance is positive. Subsequent tasks will be delayed as a result.

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