Updated: Mar 2
Many different challenges can influence your team’s ability to determine an accurate estimation. From my own experience, I've seen the following:
I do not have a degree in psychology, but I think we can agree that we tend to be either optimists or pessimists as humans. People who are good at estimating tend to be realists.
The ego that destroys everything
If you have ever been part of an Agile estimation process within an Agile team, you should already know there is always ego between team members. One classic example to illustrate it is the team ‘expert’ who knows better than anyone else and therefore dismisses other people’s opinions (no matter if they are right or wrong).
Failure to adopt the relative estimation model
Relative estimations are a common and compelling practice in the Agile process. However, it takes time for Agile teams to understand its real meaning and different techniques and methods to use it.
Dependencies (internal & external)
In a project, there are many dependencies (external suppliers, integration with another team, dependencies between stories, etc.) for the team to consider as part of their estimation process. Dependencies significantly impact the team’s ability to estimate a specific story because the team is not depending only on themselves anymore.
Uncertainties that lead to false judgment
Uncertainties have a decisive part in any estimation process, and it's essential to understand that, as they may directly impact the team’s judgment throughout the estimation process.
The impact is usually reflected in a team member who feels very uncomfortable and insecure. This results in him blowing up his estimation. Hence, it covers the worst possible scenarios, thus directly impacting the overall number of stories the team can commit to within the boundaries of their capacity.
Working under pressure
Within any project, pressure can come from various places, such as:
Pressure by management to estimate less/more time to complete a particular story because of an economic and political agenda.
Pressure arises from the team itself or stronger personality bullies from another team. These also affect the ability of the team to conduct an effective and practical estimation process.
Pressure from external stakeholders such as other teams involved in the project, Sales department or support that need the team to resolve customer issues ASAP.
Cross-functional teams are just a slogan.
In theory, a Scrum team is built from a set of people. Combined, they have the necessary skills and knowledge to estimate stories and deliver them. However, it takes time to make such teams, and even then, they may still lack all the knowledge needed to run an effective estimation process.