How often does this plan beat the deadline?

A deadline you cannot move changes the question from what date will this finish to how often does it finish in time. Ten tasks, two streams, and one number you can take into the expedite conversation.

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.

Operations Intermediate Schedule Risk Pro engine

Install free (opens the Google Workspace Marketplace in a new tab) How schedule risk analysis works

After you install, this is the model to open.

Will We Be Ready for Peak?

  1. 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.
  2. Click Start from a template and put that name in the search box.
  3. 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 when peak starts
68% of 20,000 trials finish inside the 48-day runway
The 80% date
49.6 days 1.6 days past a start that cannot move
The plan's own answer
42 days likely durations added down the stock stream
What to expedite
stock its chain drives the finish in 77% of trials, hiring 23%

Ten tasks of peak preparation and a start date that does not move. Two streams matter: stock, from locking the range through the supplier lead time to inbound and the carrier test, and hiring, from posting the roles through interviewing to onboarding. Add up the Likely column down the longer of the two and the programme takes 42 working days against the 48-day runway written beside the table, so the plan is six days early and everyone relaxes.

Click Run on 20,000 trials. The Completion Percentiles ladder is the answer: the 50% row says 46.2 days, the 75% row says 48.9, the 80% row says 49.6 and the 95% row says 53.1. Now read the 48-day runway against the ladder: day 48 clears the 50% row by nearly two days and falls short of the 75% row, so the programme that looked six days early is ready somewhere between one run in two and three runs in four, and the finish you can promise at 80% confidence is 49.6 days, a day and a half past the runway.

That bracket is the number the expedite conversation needs. It is not available from any single run of the plan, because a plan run once gives you a date and never a frequency. The criticality table then names where the risk is. The stock stream drives the finish in 77 of every 100 trials and the hiring stream in 23, so both matter and one matters more.

The racking work never drives the finish in a single trial, which is permission to stop asking about it in the weekly call and to move that attention onto the supplier. Second run, and it is the one that pays for the template. Buy the expedited freight: change the pessimistic estimate on the supplier lead time from 34 days to 24, leave everything else alone, keep the seed at 7, and run it again.

The 80% row comes in from 49.6 to 47.3, inside the runway with most of a day to spare, and the 90% row from 51.5 to 48.6, so a day-48 finish that sat between the 50% and 75% rows before the expedite now sits between the 80% and 90% rows. Two rungs of the ladder, bought by cutting the worst case on one task rather than by making the average faster.

That is the shape of every deadline problem: you are not buying speed, you are buying the removal of a tail, and the price of an expedited freight contract now sits next to a P80 that moved from a day and a half late to most of a day early. What this cannot tell you is what happens if you miss. Being one day late for peak is not the same as being one day late for anything else, and this sheet reports a probability rather than a cost, so pair it with a risk register on the same programme if you need both.

To adapt it, put your own tasks and three-point estimates in, write your own runway in working days beside the table, and read it against the whole Completion Percentiles ladder rather than against the P80 alone: the highest confidence row that still finishes inside the runway is the promise the plan supports.

The model

It arrives on a tab called Template: Will We Be Ready for Peak, carrying these columns:

  • ID
  • Task
  • Predecessors
  • Optimistic (days)
  • Likely (days)
  • Pessimistic (days)

Once it is in your sheet

  1. The model arrives with real numbers in it and runs as it stands, so you can press the button first and understand it second.
  2. 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.
  3. 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

Every model like this one, and the method behind them: Schedule risk analysis.

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