When I first started writing this series, my plan was to write about a new bias each day. To be honest — I underestimated how long it would take me to complete the other tasks that I’d laid out for myself on a given day. Anyway, so today yesterday I’d planned to talk about the framing effect, but since I so conveniently demonstrated the planning fallacy, I thought I’d talk about it.

The consequence of this post being written/published today is directly related to my falling into the trap of the planning fallacy. I planned for the completing of my other tasks to take a certain amount of time. When that time lasted longer than I had anticipated, I had no time left to write about a bias in judgment and decision-making. The planning fallacy is our tendency to underestimate how long we’ll need to complete a task — especially when we’ve had experiences where we’ve underestimated similar tasks.

This is something that even the best of us fall prey to. In fact, one of the biggest names in cognitive biases Daniel Kahneman (Nobel Prize in economicsbut a PhD in psychology!) has said that even he still has a hard time with the planning fallacy. Of course, this doesn’t make it permissible for us not to try to prevent the effects of the planning fallacy.

Before we get into ways for avoiding the planning fallacy, I want to share an excerpt from an oft-cited study when discussing the planning fallacy [emphasis added]:

Participants were provided with a series of specific confidence levels and were asked to indicate the completion time corresponding to each confidence level. In this manner, the participants indicated times by which they were 50% certain they would finish their projects (and 50% certain they would not), 75% certain they would finish, and 99% certain they would finish. When we examined the proportion of subjects who finished by each of these forecasted times, we found evidence of overconfidence. Consider the academic projects: only 12.8% of the subjects finished their academic projects by the time they reported as their 50% probability level, only 19.2% finished by the time of their 75% probability level, and only 44.7% finished by the time of their 99% probability level. The results for the 99% probability level are especially striking: even when they make a highly conservative forecast, a prediction that they feel virtually certain that they will fulfill, people’s confidence far exceeds their accomplishments.

There were a lot of numbers/percentages offered in the excerpt, so I’ve also included a visual representation of the data in a graph below. This graph comes from a book chapter by a couple of the same authors, but it is about the data in the preceding excerpt.

Ways for Avoiding the Planning Fallacy

With the first three biases I talked about, awareness was a key step in overcoming the bias. While you could make that argument for the planning fallacy, one of the hallmarks of [the fallacy] is that people know they’ve erred in the past and still make the mistake of underestimating. So, we’ll need to move beyond awareness to help us defend against this bias.

1) Data is your friend

No, I don’t mean Data from Star Trek (though Data would probably be quite helpful in planning), but now that I think about it, Data (the character) might be a good way to position this ‘way for avoiding the planning fallacy.’ For those of you not familiar, Data is a human-like android. In thinking about this way for avoiding the planning fallacy, think about how Data might estimate the length of time it would take to complete a project. It would be very precise and data-driven. Data would likely look at past projects and how long it took for those to be finished to decide the length of time needed for this new project. To put it more broadly, if you have statistics on past projects (that were similar) absolutely use them in estimating the completion time of the new project.

2) Get a second opinion

When we think about the project completion time of one project in relation to another project, we often think about the nuances that make this project different from that project — and by extension — why this project won’t take as long as that project. Planning fallacy. If you can, ask someone who has experience in project completion in the area for which you’re estimating. When you ask this person, be sure not to tell them all the “various ways why this project is different,” because it probably isn’t and it’s only going to cloud the predictive ability of the person you’re asking. You’re probably going to hear an estimate that’s larger than you thought, but I bet you that it’s probably a lot closer to the real project completion time than the estimate you made based on thinking about the ways that this project was going to be different than all the other projects like it.

This article originally appeared on Jeremiah Stanghini and has been republished with permission.