Conclusion

Professional software developers know how to provide the business with practical estimates that the business can use for planning purposes. They do not make promises that they can’t keep, and they don’t make commitments that they aren’t sure they can meet.

When professionals make commitments, they provide hard numbers, and then they make those numbers. However, in most cases professionals do not make such committments. Rather, they provide probabilistic estimates that describe the expected completion time and the likely variance.