Uncertain Dates Overview

Uncertain Dates Overview

Even if you know exactly when a particular task is going to start (see the bottom of this post), if you are uncertain about how long it will take, you will be uncertain about the date when it will finish.

Behind the scenes, LiquidPlanner does the difficult statistics to calculate these dates. There are four important dates that we calculate for you…

• Earliest Finish (10% chance of getting done before this date)
• Expected Finish (50% chance of getting done before this date)
• Latest Finish (90% chance of getting done before this date)
• Finish 98% Confidence (98% chance of getting done before this date)

If these fields are not displayed on the estimate tab, see the customizing columns help topic. We calculate these dates for all tasks, projects, and categories.

We’ll start with the expected date since that’s easiest to understand.

– Expected Finish (50% chance)

If you have an accurate estimate you can expect to finish before this date about half the time. It is kind of the “even money bet” of the schedule. It does not mean that you are 50% likely to finish on this date. Just that you are 50% likely to finish on or before this date. Which of course implies you have a 50% likelihood of finishing after this date.

– Earliest Finish (10% chance)

This is the earliest you could conceivably finish this task (or project, or category) if your estimate is accurate.

If you are looking at a single task then it corresponds to the best-case (low) estimate. For a project or category it corresponds to the date on which you are 10% likely to have finished. This takes into account all of the tasks assigned to all of the different people.

– Latest Finish (90% chance)

This is the latest you are likely to finish this task (or project, or category). If you are looking at a single task then it corresponds to the worst-case (high) estimate. For a project or category it corresponds to the date on which you are 90% likely to have finished. Like all these dates, this takes into account all of the tasks assigned to all of the different people.

Taken together, the Earliest Finish and Latest Finish give you an 80% confidence interval. That’s a fancy-pants way of saying that you’re 80% likely to fall somewhere between those two dates.

– 98% Finish (98% chance)

This is the latest you could conceivably finish this task (or project, or category). Again, that’s provided you are an accurate estimator. It is the date on which you are (unsurprisingly enough) 98% likely to have finished. This takes into account all of the tasks assigned to all of the different people.

Earliest Start

The earliest start is the soonest you are 10% likely to start this particular task. Because you can’t really start a task until preceding task completes (ideally) the actual start date of the task is uncertain. To de-clutter your display we chose to show this as the earliest LiquidPlanner thinks you might be starting this task rather than a range of possible start dates. After all, it is usually the end date you’re really concerned about.