Effort Estimates for a Cup of Coffee

I always have the same problem with my IT manager. Every time I ask for an estimate, he comes up with a huge number. On the other side, my marketing people always come up with a very optimistic figure. So I decided to make a little test. I asked my marketing manager how long it would take to make a cup of coffee. "Less than thirty seconds" she replied.

I then asked my IT manager the same question. He divided the task into small subtasks, and estimated each one of them:

• Open the cupboard - 2 sec
• Take a mug and place it on the table - 2 secs
• Close the cupboard - 1 sec
  
• Pick the jar - 1 sec
• Take out the jar lid - 1 sec
  
• Place the lid on the table - 1 sec
• Place the jar under the tap - 1 sec
• Open the tap - 1 sec
• Wait for the jar to fill up - 15 secs
• Place the lid back on the jar - 1 sec
• Place the jar on the table - 1 sec
• Press the ON button - 1 sec
• Wait for the water to boil - 30 secs
• Open the cupboard - 1 sec
• Take the coffee jar - 1 sec
  
• Place the coffee jar on the table - 1 sec
• Close the cupboard - 1 sec
• Open the drawer - 1 sec
• Take a spoon - 1 sec
• Close the drawer - 1 sec
• Open the coffee jar - 2 secs
• Fill the spoon with coffee - 1 sec
• Place the coffee inside the mug - 2 secs
• Close the coffee jar - 2 secs
• Place the coffee jar back in the cupboard - 5 secs (includes opening, etc)
• Take the water jar - 1 sec
  
• Fill the mug - 5 secs
• Place the water jar back in its place - 2 secs
• ... (the list goes on: add sugar, add milk, stir, wash the teaspoon, wash the mug, which itself consist of over ten taskst, etc)

When the list was complete, it added up to over 10 minutes. "Wait," said the IT guy. "We still have to compute the proportional part of the effort taken by the purchase of coffee, cleaning up, etc. And of course, we should not forget that preparing this estimate took some 10 minutes, over how many cups should we divide that? And should we take this conversation into account? On second thoughts, I may have been too optimistic in some of the tasks. Taking everything into account, I would price it based on 30 minutes. If we add another resource we could bring the time down, but the cost would go up"

"No wonder we are losing business" I said while I was sipping my third cup of coffee that morning.

The lesson: if you divide the task into small enough tasks, any estimate will look too optimistic.