Estimate means a guess of what the size, value, amount, cost, etc. of something. In other words, a judgment or calculation of approximately how large or how great something is.
Simply put, it means what you believe the cost, size, value, etc. of something is, although you do not know for certain.
Estimates are called estimates because they are not precise measurements or exact calculations. They are based on assumptions, probabilities, and educated guesses, which means that they may not be entirely accurate.
Software Estimation has always been challenging because of various factors such as assumptions, past experiences, expertise level, biases, over/under enthusiasm, etc.
Software estimation is critical for budgets, resource allocation, product roadmap, build v/s buy decision-making process, and others.
Here are some estimation techniques I have worked with over the years and their pros, cons, and best suited for the type of project information.
- Expert Judgment
Expert judgment is a straightforward and fast estimation technique that relies on the expertise of the estimator or a group of experts. This technique can be useful when there is not enough data available, and it requires a quick estimate of the project.
Pros: Quick and easy, relying on the expertise of the estimator.
Cons: Can be biased and inconsistent if the experts have different levels of experience or knowledge.
Best for: Small Projects or need to provide ballpark estimates.
- Bottom-up Estimation
Bottom-up estimation is a detailed estimation technique that provides a more accurate estimate by breaking down the project into smaller and more manageable tasks. The advantage of this technique is that it can provide a detailed estimate that can be used for project planning.
Pros: Provides a detailed estimate, and can be used for project planning.
Cons: Can be time-consuming and may not be feasible for large and complex projects.
Best for: Medium to large projects, where a detailed estimate is required, and the project has a defined scope.
- Three-Point Estimation
Three-point estimation is a technique that considers uncertainty by providing three estimates: the best-case scenario, the worst-case scenario, and the most likely scenario. This technique can be useful for risk management and can help identify potential issues early in the project.
Pros: Considers uncertainty and can be used for risk management.
Cons: Can be time-consuming and may not consider all factors that can impact the estimate.
Best for: Projects with high risk & uncertainty.
- Function Point Analysis (FPA)
Function Point Analysis (FPA) is an objective estimation technique that measures the size and complexity of a software system based on the functionality provided.
Pros: Provides a consistent and objective estimate, and can be used for benchmarking.
Cons: Can be time-consuming and may not consider all factors that can impact the estimate.
Best for: Large & Complex projects, where the scope is not well-defined, and a benchmarking estimate is required.
- Agile Estimation
Agile estimation is a collaborative and iterative approach that involves the entire team in the estimation process. This technique can lead to more accuracy and buy-in from the team, and can also help identify potential issues early in the project. However, Agile estimation can be time-consuming, requires a lot of communication, and may not be suitable for all projects.
Pros: Collaborative and iterative approach, involves the entire team in the estimation process, which can lead to more accuracy and buy-in from the team.
Cons: Can be time-consuming, requires a lot of communication, and may not be suitable for all projects.
Best for: Projects where the scope is not well-defined, and the requirements are likely to change during the project due to iterative feedback loops.
There is a hybrid approach to software estimation technique that I have used for 5+ years now and found it better & more accurate compared to the others.
Let me know your thoughts in the comments on
1. The above techniques
2. Your experience with these techniques or any other techniques
3. Whether you are interested in the technique that has given me close to accurate estimates across all types of projects?