Why estimating time is hard

Just the other day we were working on an internal content project (one of these very posts, in fact). We were talking deadlines. “Hey Adam, when do we want this done?” Adam answered, “I want to say the end of March, but I know I’m going to be a bottleneck.” 

Adam knew that his hope for getting it done in March was a bias working against his accurate estimation of time. He was calling out his hope, and also his conjunctive events bias. 

Conjunctive bias, or the tendency to believe that two events that have to happen together will happen together — in this case, the month ending and the post being written, edited, reviewed, uploaded, then published — is one of the biggest obstacles in accurately estimating time during project planning. Knowing how the brain thwarts us helps us work around it. 

Conjunctive events bias makes us overly optimistic

When we know something needs to happen, we’re more likely to assume it will happen. We’re overly optimistic, and that makes it hard to estimate actual time. 

That’s because our brains are more likely to overestimate the likelihood of two events happening together. When we pause and break it down, it’s easy to see how flawed that is: the likelihood of two things happening is always going to be less than the likelihood of just one of those things happening. But, our brains jump that logic — if they have to happen together, they will! 

Daniel Kahneman gives an example of conjunctive events bias in Thinking, Fast and Slow. Students were asked to estimate which statement was most likely true: Linda is a bank teller; or Linda is a bank teller and is active in the feminist movement. Most of the students (we’re talking 85–95% of them) said the second was more likely even though, logically, a broader topic is more likely to be true than a more specific one. The key here is that Kahneman’s students thought that it was highly likely that Linda is active in the feminist movement, so they were more likely to pick that option, even if it required attaching that she is a bank teller. Sure, why not! 

It’s this willingness to accept pieces that don’t necessarily fit in order to get an outcome we want that’s at the heart of the issue when building out timelines. When we want a blog post to be done in March, the brain sides with that outcome and bypasses its criticality about any other piece of information that’s not going to result in that outcome. 

This is all the more true for the type of holistic, multi-stage engagements we do: custom web apps, website redesigns. Every step has a chance of going wrong in some way — human foibles, technological errors, a bizarre weather event. With each added step, the “firm deadline” on a project becomes less likely because the stack of events that have to happen together keep building up.  But our brains don’t want to buy it. They want us to be on time, on budget, and error-free.

When certain events need to take place to achieve a desired outcome, we’re overly optimistic that those events will happen. 

Farnam Street, Unlikely Optimism: The Conjunctive Events Bias

It’s more likely that things won’t line up perfectly, that things won’t go according to the plan, that a change in one component will impact other parts of the project. This is true for all businesses everywhere, and definitely agencies like ours. This isn’t to scare off any potential clients reading this! When we’re honest about what can go wrong — and what likely will —  we can make better plans that accommodate for those setbacks.

How we overcome optimism and plan accurately

Acknowledge our optimism: The first step in solving your problem is admitting you have one. When that problem is optimism, it can sound like, “Our goal is to have the project launched on April 15th. We want to hit that deadline, and we think it’s possible.” Or, “We’d love to say yes to this project.” 

Admit our assumptions: As much as possible, we articulate the assumptions we’re using. It’s as simple as saying, “If step A and B go as planned, step C will be done by March 30. That’s our drop-dead for an April 15 launch.” 

Practice some pessimism: Admitting our assumptions makes it easy to ask the next question, “What if A doesn’t go as planned?” There’s a lot less doom when you do this at the beginning of a project than if you were to think about the disaster only as its striking. With time you can build in pressure release valves and contingency plans. 

Record our decisions: Writing down the logic that led to each decision helps us if we need to roll with the punches later down the line. It also helps us during a postmortem: we have a record of what we thought then, so we can accurately prevent that mistake in the future. Without this record, it’s easy to invent a totally new narrative of how we got to a decision.  

Our POV: Realistically, things are likely not going to go as planned

This is not us admitting we’re not confident in our abilities. The opposite is true. It’s our confidence and our experience that makes us able to openly say that, while we’d love to be optimistic about everything, we’d rather be accurate. (And for all of you keeping score at home: the post went live in April, but Adam wasn’t the bottleneck. It was Emma!)