Time estimation method of the hottest project

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Project time estimation method

this chapter continues the introduction of the schedule in Chapter 7. This chapter mainly introduces time estimation and how to speed up the completion of the project

type of time estimation

there are usually some errors in time estimation. Your goal is to understand the degree of errors. The schedule of any project requires knowing (or estimating) the time of each activity or task. Because, according to the definition of the project, any project has a one-time feature. Therefore, such estimation must be inaccurate (the only way to ensure that the time estimation is met is to estimate the time infinitely long, but if so, the project will not be approved)

after collecting the work breakdown structure and milestones required to make the project plan, you also need to evaluate their accuracy. How can you judge whether the estimation of each component of the project is vague, reasonable and too conservative? Although some projects can be based on similarities with the past, many projects are different from the past, or need to develop new technologies or new processing methods, so it is difficult to accurately estimate them. All you can do is to make the time estimation as accurate as possible. If you estimate a large number of tasks in this way, overestimation and underestimation of time and cost will offset each other. If your team estimates many tasks, assuming that there are some random, less, over or under estimation errors for a single task, the total time estimation error rate of the project will be reduced. If some tasks in your project are the same or similar to those in the previous project, it will be easier to estimate (as mentioned in Chapter 6, one of the purposes of splitting the project is to make the task easier to understand, but also to make it easier to estimate). There are two methods of estimation: pert and practical method. However, please remember that there are two problems when time estimation is performed to improve the effective resolution at the expense of dynamic performance (bandwidth): first, for a given task, it is necessary to determine the number of labor hours it requires (this may depend on the specific skill level of the personnel); Second, we should determine the duration of this activity. To plan expenses and manage projects, you must understand the former, while the latter is used to determine the overall project schedule. However, when you need a resource that may not be available at that time, you should take this situation as an estimation assumption and include it in your problem management and possible sources of risk

don't exaggerate the task duration and cost

exaggeration is a way of risk identification - overestimating the duration of a task and the amount of human input spent in order to prevent unknown things. Some people also call this behavior "filling fat". Unfortunately, this phenomenon often occurs in real life, but more and more organizations are aware of this problem and prevent it from happening. Some reasons for blocking are listed below

. Due to exaggerated estimation, it is difficult to distinguish how much of the estimated data is false. Therefore, the baseline used by the project manager to track actual performance is wrong. Functionally, exaggerated estimation will lead to two distorted activities in project management: estimation and budget

. generally speaking, everyone likes to finish the work at the last minute of the estimated time, which leads to the working time easily exceeding the estimate. From then on, the task of controlling the project is controlled by each performer, not by the project manager

· if everyone exaggerates more than one person, it will lead to the wrong critical path of confirmation

. people will only focus on "gambling" instead of exploring the reasonable validity of assumptions. Eventually, everyone will not believe any estimates, and the corporate culture will become worse

· if you apply these exaggerated miscalculations to some types of government contracts, it will push you and your organization to the path of felony. Therefore, be sure to thoroughly understand the policies of your state in terms of estimation and risk reservation before you submit estimates to the government

pert time estimation method

pert network originates from items with uncertain activity time. Solving this problem requires three time estimates for each activity

(1) most likely time of activity (TM)

(2) optimistic activity time, that is, the shortest time (to) required to carry out this activity

(3) pessimistic activity time, that is, the longest time (TP) required to carry out this activity

see Figure 8-1. We can calculate the expected time (TE) of the activity. This calculation is a reasonable estimation method. You can also calculate the uncertainty of time, which we call "standard deviation", and the calculation method is shown in the figure below

The figure

shows how to calculate the expected time of a path and the standard deviation of the expected time of that path. The significance of the calculated standard deviation is the same as that of the normal (Gaussian) probability distribution: in 2/3 time, the work will be completed within the expected time plus or minus one standard deviation; In 95% of cases, the work will be completed within two standard deviations; In 99% of cases, the work will be completed within three standard deviations. When the project delay will be subject to cost penalty, this calculation is very important and helpful because you can estimate the possibility of delay

the figure shows three time estimates of a certain path containing three activities. After completing the calculation of this case, the expected time shown in the result is 29 days, and the standard deviation is 6 days. Therefore, in the case of 2/3, the project will be completed between the 23rd and 35th days

people have found that it is best to let people outside the e-commerce team make three time estimates (optimistic time, pessimistic time and possible time), and then according to the question - "tell me why this is the most optimistic time estimate point? What is your implied assumption?", For more information. This questioning style can make others think that you are asking for help, not interrogating them. Those who use this method will find that they can better obtain information and have a better working relationship with other people or teams

it takes a certain amount of energy to calculate the expected time and standard deviation for the three time estimates. Many project management software can calculate these PERT time estimates

time estimation

I recommend using consolidated practical judgment for time estimation. The task leader, project manager and other team members should discuss the task and come up with how to judge the schedule. The reason for inviting task leaders is the golden rule. The participation of the project manager is to make a trade-off between other project time estimates. Others can bring professional experience and knowledge

however, for a large project, task leaders, project managers and other team members cannot discuss every task for a simple reason: there is not so much time. In a large project, a compromise is that the project manager needs several deputy managers to represent him or attend the meeting of such task estimation

the purpose of this group discussion is to reach an agreement on the following issues, that is, if the scheduled way is carried out, how long should each task be completed. If the task leader is not very experienced, he will not complete the task as quickly as an experienced person (this person may be a consultant expert). Sometimes the opposite happens. A Junior Mechanical Engineer may complete the task quickly because of the use of B2B computer-aided design tools, while an old engineer may not use such tools at all

if a task (of course, one-time) is exactly the same as a previously completed task (or very similar), then the experience of the previous task is a good estimation guide. However, we should first confirm that there is no substantive difference between the two, otherwise the previous experience will be meaningless

the logical order of estimating a new task is: ① consult the company's project files to determine how many days and people were used for the previous similar task; ② Determine the complexity of the current project compared with previous tasks, so as to obtain a multiplier of duration and personnel; ③ The cost of the task is obtained by multiplying the number of people by the number of days and then multiplying the appropriate labor price. The premise of doing so is to assume the existence of these archives, while emphasizing the importance of retaining the historical data of the project. If there is no such information, we can only rely on memory, but everyone must remember different things

compress critical path

Chapter 3 introduces that the project manager believes that there will be great pressure to complete the project quickly, and the whole project team needs to understand the problems related to balancing needs. Establishing the critical path time will help you know whether you can complete it within the target time

it is reasonable to reschedule tasks so that they can be completed ahead of the first expected time. In a word, we should start with the tasks in the early stage of the project and reschedule them so that they can be completed as soon as possible (for the tasks until the later stage of the project when the stress reaches Zui maximum value, please keep their first time estimate to prevent unexpected problems). Therefore, please try to compress the task time with low compression cost and risk, and be careful not to create another critical path. If there is not enough time in this way, the whole project can only be rescheduled, and some tasks may need to be carried out side by side. Figure 8-5 shows some other alternatives to shorten the schedule, including negotiating simple specifications with customers, using more effective resources, and designing more efficient project plans

in integrated project management, we should adhere to the logic and integrity of the project model. The operating rules are: the schedule should be logical and the improvement should be systematic. If you use this method, there are several pressure sensors and force measuring instruments that you need to pull. You can only use lever force standard machine or static weight force standard machine to measure. The management tools you need to know can help you speed up the project, as described below

. Hypothesis analysis. Generally, the initial assumptions are conservative. As the project team has a better understanding of the project model, it can make appropriate changes to the assumptions, and everyone can "buy in". This can also be a part of project management

· follow up quickly. Quick follow-up is a method of paralleling certain stages and tasks, allowing work that is assumed in advance in sequence to be carried out at the same time as other work. This kind of schedule will increase the risk, but will reduce the trouble

· rush. As described in Chapter 3, expediting needs to provide more resources for the project in order to speed up the project

· simplification. Generally speaking, you can negotiate with customers to cancel some requirements or postpone the completion time (end)

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