Essentially, all models are wrong, but some are useful. -- George E. P. Box
I don't have any references handy, but I think this model is derived from data from large waterfall-style projects. For small projects like 1 or 5 man-months, the model may not be applicable that well. Models give you wrong results if you try to extrapolate them too far from their validity range.
Though it's also true that especially in a small project, it's not always possible to do work that contributes to deliverables. For example, when waiting on external dependencies required in order to proceed.
I have used models like these to sanity check project offers within the same size range and with similar process characteristics. Not mechanistically, but as indicators to see if there are areas in the plan/offer that require closer attention.
Also, how can you estimate optimum staffing levels from this model?
If you have and optimum duration of T months and effort of MM persons*months, you allocate the staff to complete MM work in T time. Your average staffing level is MM/T persons.
Of course, in practice having a steady MM/T staffing level is not optimal. Start with a small team to get the high-level architectural issues settled and then grow the team only after there's something useful for new persons to do.
As far as I can see for software development projects of up to 10 man-months that currently prevail within business environments (in-house projects run within non-software companies) the optimal figures produced by the model do not reflect typical durations and team sizes.
The figures for projects over 20 man-months become much more believable, especially where efforts are tightly coupled.
As a result, I'd avoid using the formula for anything but a quick order of magnitude guestimate for projects of over 20 man-months in duration. For anything less than that a quick planning session would give you a more accurate and trustworthy result.
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本质上，所有模型都是错误的，但有些模型是有用的。 -- George EP Box
我手头没有任何参考资料，但我认为这个模型是从大型瀑布式项目的数据中派生出来的。对于 1 或 5 个人月之类的小型项目，该模型可能不太适用。如果您尝试将模型推断得离其有效范围太远，模型就会给出错误的结果。
尽管确实，尤其是在小型项目中，并不总是能够完成有助于交付成果的工作。例如，当等待继续所需的外部依赖项时。
我已经使用这样的模型来健全性检查项目提供的相同尺寸范围和相似的过程特征。不是机械地，而是作为指标来查看计划/报价中是否有需要密切关注的领域。
如果您有 T 个月的最佳持续时间和 MM 人员 * 个月的工作量，您可以分配人员在 T 时间内完成 MM 工作。您的平均人员配备水平是 MM/T 人。
当然，在实践中，稳定的 MM/T 人员配置水平并不是最佳的。从一个小团队开始，解决高层架构问题，然后只有在有新人可以做的有用的事情之后才扩大团队。
Essentially, all models are wrong, but some are useful. -- George E. P. Box
I don't have any references handy, but I think this model is derived from data from large waterfall-style projects. For small projects like 1 or 5 man-months, the model may not be applicable that well. Models give you wrong results if you try to extrapolate them too far from their validity range.
Though it's also true that especially in a small project, it's not always possible to do work that contributes to deliverables. For example, when waiting on external dependencies required in order to proceed.
I have used models like these to sanity check project offers within the same size range and with similar process characteristics. Not mechanistically, but as indicators to see if there are areas in the plan/offer that require closer attention.
If you have and optimum duration of T months and effort of MM persons*months, you allocate the staff to complete MM work in T time. Your average staffing level is MM/T persons.
Of course, in practice having a steady MM/T staffing level is not optimal. Start with a small team to get the high-level architectural issues settled and then grow the team only after there's something useful for new persons to do.
与任何模型一样，没有必要盲目相信它，特别是当该模型确实很容易测试时：
据我所知，目前在业务环境中普遍存在的最多 10 个人月的软件开发项目（在- 在非软件公司内部运行的内部项目）模型生成的最佳数字并不反映典型的持续时间和团队规模。
超过 20 个人月的项目的数字变得更加可信，尤其是在工作紧密结合的情况下。
因此，除了对持续时间超过 20 个人月的项目进行快速数量级估算之外，我会避免使用该公式进行任何其他操作。对于任何比这更少的事情，快速的计划会议都会给你一个更准确和值得信赖的结果。
As with any model there is no need to take it on blind faith, especially when the model is really easy to test:
As far as I can see for software development projects of up to 10 man-months that currently prevail within business environments (in-house projects run within non-software companies) the optimal figures produced by the model do not reflect typical durations and team sizes.
The figures for projects over 20 man-months become much more believable, especially where efforts are tightly coupled.
As a result, I'd avoid using the formula for anything but a quick order of magnitude guestimate for projects of over 20 man-months in duration. For anything less than that a quick planning session would give you a more accurate and trustworthy result.