Two tasks both have slack. Can you spend it twice?
Two tasks each report sixteen days of float and it is the same sixteen days. Spend it on one and the other has none left, which is the single most common way a plan with room in it slips anyway.
Words on this sheet
- Predecessors: The tasks that have to finish before this one can start. Put their IDs here, separated by commas, and leave it blank when nothing has to come first.
- F statistic: The variation between the groups divided by the variation inside them.
- Cohort: One group who start together and are counted together: an intake of students, a class year, or the customers who joined in the same month.
School Starter Critical Path Pro engine
After you install, this is the model to open.
When Will the Course Be Ready?
- In your spreadsheet, click the Sortia icon in the strip of icons down the right-hand edge. No strip? Click the arrow at the bottom-right to open it. You can also use Extensions, then Sortia, then Open Sortia.
- Click Start from a template and put that name in the search box.
- Pick the card with that name and click Load this template. It arrives on a new tab with real numbers already in it.
This one runs on a Pro engine, and every free install includes five full-quality runs on your own numbers, shared across all five Pro engines rather than five for each. After that, Pro is $199/year.
The answer
- Ready on day
- 52 set by the outline, writing, video and pilot path
- Critical
- 6 of 8 tasks: a day lost on any of them is a day on the launch
- The slack
- 16 days on the quiz and LMS path, shared, not 16 each
Eight tasks and two streams. Content runs from the outline through scripting, recording and the accessibility check. Assessment runs from the outline through the quizzes and the learning platform setup. Both have to be finished before the pilot. Click Run and the course is ready on day 52, driven by the content stream, and the report shows 16 days of slack on the quiz build and 16 days of slack on the platform setup.
Two tasks, sixteen each, and here is where plans go wrong: that is not thirty-two days of room. It is sixteen days, once, shared by both because they sit on the same chain. Total float belongs to a path, not to a task, and the report shows it against every task on that path because any one of them could use it. Prove it in one run. Change the quiz build from 10 days to 26, which is what happens when the assessment design gets a rewrite, and run again.
The finish is still day 52, so the deadline held. But the report now says every task is critical, 8 of 8, where it said 6 of 8 before: the quiz build has no slack left and neither does the platform setup. Every day of buffer on that stream has been spent, and the next surprise anywhere on it moves the launch. Nothing warned you, because the first run said sixteen and the second run said zero and nobody looks at slack twice.
Two habits follow. When you read a slack figure, look at what else is on the same chain before you promise any of it away. And when two people are each told they have three weeks of room, check whether they have been told about the same three weeks. Note also that captions and transcripts for six modules of video is a real six days and it sits on the critical path, which is worth seeing before somebody proposes doing it after launch.
What this cannot tell you is how much of the content stream is really sequential. If your scripts can be recorded module by module rather than all at once, the whole shape of this plan changes. To adapt it, put your own tasks in with their IDs and predecessor IDs, keep the accessibility work on the plan rather than after it, and read slack by chain rather than by task.
The model
It arrives on a tab called Template: Course Build, carrying these columns:
- ID
- Task
- Predecessors
- Duration (days)
- Owner
Once it is in your sheet
- The model arrives with real numbers in it and runs as it stands, so you can press the button first and understand it second.
- Change the numbers to yours. The sheet marks which cells are inputs and which hold formulas, and most labels carry a note explaining the row.
- Press the run button at the bottom of the panel. It is labeled for the tool you are in, and the result lands on its own tab, with a written reading of it beside the figures.
Never used Google Sheets? Start here goes the whole way, in seven steps, and assumes nothing.
Next question
- What are the odds you land an A?What Grade Will You Get?
- Exactly what do you need on the final?What Do You Need on the Final?
- Do the decision rules agree on what to build?Which Option Wins, and at What Odds?
- Three averages differ. Is that more than chance?Which Study Method Actually Works?
- Should you switch doors or stay?Switch or Stay? The Monty Hall Problem, Simulated
- Why does splitting the money cut the risk?Why Diversification Works
Every model like this one, and the method behind them: Schedule risk analysis.