Double Dependencies, Double Delays

My friend’s triplets taught me about project management.

“You know,” said Seamus, “I’m so grateful to have a healthy wife and three healthy boys. But I’m also grateful to now have the perfect excuse.”

“What do you mean?” I spluttered, spilling coffee down my shirt.

“With three kids, there’s a 87.5% chance that I won’t leave the house on time. That gives me the perfect excuse to be late to events that I don’t actually want to go to.”

“Why 87.5%?”

Seamus raised his index finger. “Say I had just one kid. In that case, there’d be a 50% chance that he’d be ready when we need to leave the house, and a 50% chance that he wouldn’t. That really only gives me an excuse to be late 50% of the time. With me so far?”

I nodded, rubbing my stained shirt.

Seamus raised two more fingers, “But I have three kids - Alvin, Simon and Theodore. That means there’s a much greater chance that at least one of them won’t be ready when we need to leave. A 7-in-8 chance, to be exact.”

“So that’s the 87.5%. But why so high?”

Seamus pulled out some paper, and a baby wipe for my shirt.

“If you imagine each of my kids can either be ready or not ready when we need to leave, there’s actually 8 permutations. And only one these permutations is one where all three of my kids are ready on time.”

“Oh” I said, as something in my head clicked.

Troy Magennis suggests that “every dependency (kid) doubles your chance of being delayed”.

Businesses often organise themselves around specialisms - separating developers into one team, business analysts into another, and so on. This means that each project will have dependencies on many teams.

Many businesses also create conditions that cause teams to deliver slowly and unpredictably.

It is a common belief that keeping staff busy means that more work will be delivered in any given period. Unfortunately, by encouraging staff to work on many items in parallel, staff must continuously context switch. This increases the chance of mistakes that are caught late and take time to fix.

Kingman’s formula also reminds us that, when staff utilisation approaches 100%, queue lengths grow towards infinity - keeping projects waiting.

So, many businesses unintentionally design themselves so that each project has many dependencies that are prone to long waits and unpredictable delays.

The takeaway? As Dominica DeGrandis suggests, “Every dependency you can find and eliminate doubles your chances of delivering on time”. So, have more kids for a better excuse - but don’t name them after chipmunks.