《Fundamentals of Project Management 4th Edition》 读书笔记 第六章 使用WBS

CHAPTER 6 Using the Work BreakdownStructure to Plan a Project

识别任务最有用的工具就是WBS，背后的思想是：你可以将一个复杂的任务分解为多个小任务，知道不能再分。对小任务的估算要容易。估算后再进行汇总。

The most useful tool for accomplishing allof these tasks is the work breakdown structure (WBS). The idea behind the WBSis simple: You can subdivide a complicated task into smaller tasks until youreach a level
that cannot be further subdivided. At that point, it is usuallyeasier to estimate how long the small task will take and how much it will costto perform than it would have been to estimate these factors for the higherlevels.

对以前未从事过的任务，我们并不擅长进行估算。估算肯定会出错，这些错误要随着项目的推进而不断改正。

Nevertheless, it is still not easy toestimate task durations for activities that have never been performed before.Because this is the typical situation in engineering hardware and software developmentprojects,
we might expect many of these estimates to be in error, and thisseems to be demonstrated by experience. Still, the work breakdown structure makesit easier to estimate knowledge tasks than any other tool we have.

停止进行WBS，直到一个能够进行精确估算的层次。

Stop breaking down work when you reach alow enough level to do an estimate of the desired accuracy.

首先要考虑是谁来完成这个任务，其次要基于历史数据进行估算。

You cannot do a time or cost estimate withoutconsidering who will actually perform the task. Second, you must base theestimate on historical data or a mental model. Historical data are best.

一旦要做的任务被识别出来，下一步就是估计任务所需的时间和资源，这叫做估算。

Once tasks have been identified, the timeand resource requirements must be determined. This is called estimating.

帕金森定律：工作总是会被延长至它被允许的时间限制处。

Parkinson’s Law: Work expands to fill thetime allowed.

一个原因是，人们觉得还有时间上的剩余，所以他们对已完成的工作进行改进。另一个原因是，人们认为如果这次完成早了，下次就会要求以更短的时间完成，并被分配更多的任务。有一个非常重要的关键点需要注意：如果人们认为他们效率更高会受到某种形式的惩罚，他们就不会进行高效工作。所以不能一味地压缩工期，对那些提前完成工作的人，不要分配给更多的任务。

One reason is that when people find themselves with some time left, they tend to refine what they have done. Another is that people fear that if they turn work in early, they may be expected to do thetask
faster the next time or that they may be given more work to do. This is avery important point: If people are penalized for performing better than the target, they will quit doing so. We must be careful not to penalize workers whoperform better than expected
by loading them down with excessive work.

一个项目失败的原因是：将大致的估计变为了实际的目标。

One of the primary causes of project failuresis that ballpark estimates become targets.

一些估计上的指导：

Here are some guidelines for documentingestimates:

估计带上公差

[1]Showthe percent tolerance that is likely to apply.

记录估计基于的假设

[1]Tell how the estimate was made and what assumptions were used.

记录可能未来会影响速算准确度的因素，一旦这些因素开始生效，就要重新考虑估算。

[1]Specify any factors that might affect the validity of the estimate (such as whether the estimate will still be valid in six months).

时间估算的新方法。3个以上的人，每人实现将任务估计的值写到纸上不给大家看，然后统一亮出。有大偏差的话，要进行集体讨论原因。最后达成一致。

In recent years, a new method of estimatingknowledge work has been developed that seems to work better than oldertechniques. Rather than have individuals estimate task durations, the new method asks at least
three people to estimate each activity in the project that they know something about. They do this without discussing their ideas with oneanother. They then meet to find out what they have put on paper.

In a typical situation, there may be arange of times, such as, for example, ten days, twelve days, and thirty days,in which two of the estimates are close together, but one is very different.How do you handle
the discrepancy? The best approach is to discuss what eachperson was considering when he made the estimate. It may be that the person whoput down thirty days was thinking about something that the other two had overlooked. Or, conversely, the other two might
convince the thirty-day personthat his number is way too high and get him to come down to a figure nearer their estimates. In any case, they try to arrive at a number that they all can support.

This is called consensus.

这样估算有3点好处：1、集体估计，避免个人带来的偏差；2、没有经验的人可以借此学习；3、多人想到的东西会更多。

There are three advantages to thisapproach. First, no one person is on the hook for the final number. Second, inexperienced people learn to estimate from those more experienced. Third, severalpeople are likely
to collectively consider more issues than any one person would do working alone. For that reason, you are more likely to get an accurate estimate, although it is important to remember that it is still by definition notexact!

对于估算要有记录，并在任务完成后进行回顾反馈，进而不断改善估算的准确性。

People cannot learn unless they receive feedback on their performance. If you went out every day and ran one hundred yards, trying to improve your speed, but you never timed yourself, you wouldhave no idea
whether you were getting better or worse. You could be doing something that slowed you down, but you wouldn’t know it. In the same way, if you estimate task durations but never record the actual time it takes to do the task, you are never going to get better
at estimating. Furthermore, you have to track progress by recording times daily. If you record times once a week, I canpromise you that you will be just guessing, and that won’t be helpful.