What is a scheduling error and how to properly estimate deadlines

What is planning error

Over the past three years, I have painted five rooms in my home. I started with the bedroom and planned to handle it in a week. However, the final touch was made only a month later.

Do you think, having started the second room, I have foreseen a month to paint it? But no. I was sure: since I had already filled my hand, then I would definitely finish by the weekend, maximum - by the next. But it took me a month again. As with each of the other rooms. Besides the kitchen, it took even longer.

Every time, preparing to paint the next room, I expected that in a week or two everything would be ready. Experience told me that I would never do it in less than a month. However, it was difficult to give up the confidence that this time things will definitely go faster.

This overconfidence that makes us underestimate the time we need to solve problems has a name: planning error. This concept was introduced in the late 70s by psychologists Daniel Kahneman and Amos Tversky.

Scientists explained that when planning, people often ignore their past experiences. In my case, it was the fact that it took me a month to paint the room each time. Usually we focus only on the task ahead: this room is small, which means that it will not take long to paint it.

Daniel Kahneman talks about this in detail in the book Think Slow … Decide Fast. He argues that planning errors are usually related to two things:

We do not consider how long it took us to complete similar tasks in the past.
We assume that we will not face complications that cause delays.

What does a misjudgment of time lead to?

According to the Project Management Institute, just over half of all projects are completed on schedule.

But it's one thing to underestimate the amount of time it takes to paint a room (it'll just give you a little inconvenience). It’s quite another to make the same mistake in evaluating work tasks and projects. Here the consequences can be much more serious.

At best, this will result in you or your team having to work overtime. At worst - to a lack of budget, small profits, dissatisfaction with bosses and customers.

How to evaluate tasks correctly

You need to stop planning, trusting one intuition. Better to use special techniques.

1. Build on previous experience

Psychologists Kahneman and Tversky recommend: before starting work, you need not only to assess what needs to be done, but also to estimate how much time is usually spent on such tasks.

For example, you need to create a new feature for a mobile app - find out how much time your team spent on a similar task. Want to write a 4,000 word blog post - find data on how many hours or days it took you last time.

If you're working alone, the easiest way to gather this information is to use a time tracking app. Apply it with different types of tasks, and later use ready-made reports.

For team activities, project management software comes in handy. Most of them use several methods of collecting data, for example, taking into account the actual work time and building a Gantt chart.

2. Ask someone else to rate your task

In 1994, the journal of the American Psychological Association "Personality and Social Psychology" published the results of five studies conducted by Roger Buhler, Dale Griffin and Michael Ross.

They confirmed that people often make the planning error described by Kahneman and Tversky. But something else came to light: we often misjudge the costs of our own tasks, but we can predict quite well how long it will take someone else.

The researchers asked the study participants to guess how long it would take for another person to complete a certain task. When answering, they more often referred to existing experience. And even when he was not there, their assessments were much more rational than the conclusions of those who were supposed to carry out the task.

This is because we are usually very optimistic about our abilities. And much more objective when it comes to someone else. So instead of trying to evaluate tasks yourself, ask a friend or colleague to do it for you.

3. Create a time range and take into account the possibility of delays

There are famous known - things that we know that we know them. There are also known unknowns - things that we know we don't know. But there are still unknown unknowns - these are things that we do not know about, that we do not know them.

Donald Rumsfeld American politician

This quote is often referenced in project management. To account for the unknown unknowns that Rumsfeld talks about, executives use what they call a cone of uncertainty. It is designed to display the range of time that a task might require.

Planning error and how to avoid it: the cone of uncertainty

When you first start working on a project, you still know little about it. Therefore, the actual time it takes to complete it can vary greatly from the forecast. You think the work will take two days, but in reality it may take eight. Or just a few hours.

But as the process progresses, this range shrinks. However, you can only say exactly how much time you need at the end - when the project is completed.

Still, the cone of uncertainty allows for a more accurate estimate. If you don't know much about an upcoming project, divide the estimated runtime by four to find the lower end of the range, and multiply by the same to determine the upper limit. The result will be, for example, from 1 to 16 days.

If such a wide range does not suit you, use only the upper limit for accounting - then, presumably, the work will take 16 days. This is not the most accurate number, but it is most likely closer to reality than your original prediction.

4. Rate the problem on three points

This method will help you be more objective. For each task, you need to give an assessment:

best script;
worst case scenario;
most likely scenario.

The first number will most likely match your original prediction. The assessment of the most likely scenario can be based on empirical data that you have. And when assessing the worst, you need to consider how long it will take if things go wrong.

With three numbers, calculate the average. For example, if the best scenario is three days, the probable is five days, and the worst is nine, just add: 3 + 5 + 9 = 17. Then divide that number by three. It turns out on average 5, 67 days - this is your forecast of the required time.

5. Calculate the error rate

Steve Pavlina, author of Personal Development Course for Smart People, recommends calculating the coefficient of how wrong you are in your planning. In the future, this number can be used for all your tasks.

Give an estimate of the time for several tasks that you need to complete in the near future. Write down your assumptions. After finishing work, note how much you spent in the end.

Add all the scheduled times together. Do the same with the actual one. Now divide the actual time by the original estimate - you get the ratio you want.

For example, you estimate that it will take 12 hours to complete several tasks. And in the end, we spent 15. The coefficient of error: 15/12 = 1.25. This means that the tasks took you 25% longer than you planned.

Now, always multiply your initial estimates by the resulting error factor - and they will be more accurate.

6. Conduct an assessment at the most unproductive times of the day

American analyst and business literature author Daniel Pink in his book Timehacking. How science helps us to do everything on time”plunged into research concerning our chronotypes - internal clocks.

He studied how they affect how we feel throughout the day. And I found out that chronotypes not only control our physical and mental activity, but also determine what time of day we are most creative and when we are prone to positive and negative thoughts.

Pink cites research by Scott Golder and Michael Macy, who analyzed the mood of people on Twitter. They found that user posts are usually not very positive during periods of low productivity.

For most people, this decline occurs in the middle of the day, just after lunch. According to Golder and Macy, it is unlikely that you will be in a good mood during this time. This can help you avoid overconfidence and optimism and, as a result, plan more effectively.

Thus, the essence of the latter method is to evaluate tasks while on a decline in productivity. This is about six hours after waking up. But you can just wait until the feeling of dispersion and fatigue comes.

Based on the results of the work, check if you have come close to reality by planning your time in this way.

The very understanding of the planning error will help you to correctly evaluate the tasks. You may not be able to control your tendency to overestimate your own abilities. But if you realize how excessive optimism affects, and try to reduce this influence, then you will become much better at managing your time.