Activity Duration Estimating
| One of the hardest areas for project managers to accomplish is estimating duration of activities. First, each project is a unique endeavor, so there isn't always a lot of historical information available. Second, estimating is more of an art than a science because it gives you inconsistent results. Let's discuss what PMI considers important for activity duration estimating. According to PMI, "The Activity Duration Estimating process requires that the amount of work effort required to complete the schedule activity is estimated, the assumed amount of resources to be applied to complete the schedule activity is estimated, and the number of work periods needed to complete the scheduled activity is determined" (PMBOK, p. 139). The person who is most familiar with the tasks or who is going to do the work should provide the estimates or check them because that person will be most qualified to make estimations.
The answer is C. We hire people for their expertise; we should let them use it. Allowing the project team to help with duration estimating will build buy-in from the team at the same time. PMBOK refers to this as "expert judgment" (PMBOK, p. 141). These estimates become better as the project team gains more knowledge of the project requirements. Most project management software allows adjustment to remaining work by the resource assigned to the activity or task. Thus, the project manager can go in the program and change the estimate as the requirements become clearer. This process is referred to as progressively elaborated estimates. Over time, your work estimates should converge with the actual hours used.
The answer is C. You then work off this schedule for the rest of the project. Determining who your resources are or at least what roles and experience you need on your project will influence your duration estimating. For example, an experienced senior coder should take less time than a junior coder to develop a software program. These resource roles are documented in the activity resource requirements from the activity resource estimating process. As we work with resource requirements, we must remember the Law of Diminishing Returns as applied to the efficiency of adding resources to activities in order to reduce the activity duration. For example, if it takes one painter 40 hours to paint a room, then if you add a second painter, it should take 20 hours. However, the efficiency of the two painters is 50% less, according to the Law of Diminishing Returns. More communication is needed, and they might bump into each other, causing lower efficiency. Although some programs allow you to put several people on a task and show that the time needed for the task is reduced, in reality, having too many people on a task will usually cause it to take longer. The organization that you work with or for may have some organizational assets available to help with your estimating. Estimating databases and other historical data are examples of organizational assets that might be helpful. Remember that these are guidelines, not exact values for all tasks in the new project. Records of previous projects also might be helpful for estimating. It is also important to note if the estimate missed the actual value by a great deal, which may be shown by looking at past records of similar work. At the very least, you will have a project calendar from past schedules of the organization. When project managers are faced with a similar project but have very few specific requirements, they typically will use top-down or analogous estimating. This process is usually done in the initial phases of the project. It is a form of expert judgment where past experience is used as a basis for estimating a similar new project. Another widely used method is Quantitatively Based Durations or parametric estimating. This method uses some form of parameter measurement to estimate activity durations. For example, the parameter may be lines of code per hour or feet of pipe installed per hour. One additional adjustment to activity duration that most project managers incorporate is a contingency reserve. This is additional time within the schedule of the overall project. This added time, which is based on risk, is called a time reserve or buffer.
The answer is B. Organizational process assets are useful if the information contained in the asset is close to the information you will need to successfully plan and execute a new project.
The answer is C. Analogous estimating is often used to give the first overview of potential costs and schedule for a project that is similar to a previous one. Three-Point Estimates, once called Program Evaluation and Review Technique (PERT), is a more mathematical approach to estimating activities and developing the schedule. This method uses a weighted average duration estimate to calculate activity durations. I like to use this to help team members come up with time estimates when brainstorming. These estimates have a built-in risk factor. Let's look at the formula. Each task has three estimates:
Mean formula = (P + 4M + O) / 6 Standard deviation formula = (P O) / 6 Standard Deviation is used to calculate confidence of success:
Example: Task A Duration:
Mean: 35 + (4 x 26) + 20 / 6 = 35 + 104 + 20 / 6 = 159/6 = 26.5 Standard Deviation: 35 20 / 6 = 2.5 To be 96% confident of completing this task on time: 26.5 + (2 x 2.5) = 31.5 The final activity estimate should be described in a range of durations, such as days or weeks, or in a percentage. Documentation of the "basis of estimates" or the methods and assumptions used to compute activity estimates should be included in the final activity duration estimates. Don't forget to update any activity changes that result from estimating activity durations.
The answer is C. 60 + 4 x 40 + 32 / 6 = 252 / 6 = 42. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
EAN: 2147483647
Pages: 167