Slack time=LS-ES=LF-EF: the time an activity can be delayed. The estimated activity time is calculated using a weighted average of a minimum, maximum, and most likely time estimates. Probability calculations are a feature of PERT. // As organizations flatten more will depend on projects & project leaders. -Expected Time (ET) for each activity = (a+4m+b)/6. a=optimistic, m=most likely, and b=pessimistic time.-Determine the CP using the ET (same as with original times). ET is based on beta districution, is extremely flexible, has finitie end pts and permits straightforward computation. -Calculate the variances (?2) of activity times, this is associated with each ET and is computed: ?2=((b-a)/6)2 the greater the difference btw the two extremes, the larger the ?2. -Determine the probability of completing the project on a given date: Sum the variances of all the activities on the CP. Substitute this figure along with the project due date and the project expected completion time into the Z formula: Z=(D-TE)/( ? ?2CP) ½ neg. Z value: find the corresponding pos. value and subtract from 1. D=desired completion date for the project. TE=expected completion time. ( ? ?2CP) ½=square root of sum of variances along the CP. Z=the # of ? the the project due date is from the ET. e.g. prob. that a project can be completed in 19 weeks or less Z=-0.955, so prob will be 17%. Prob. that a project can be completed in 21weeks or more (at least 21 weeks) Z=0.0947 is 54%, then subtract from 100%: 100-54=46% prob. To find duration (D) that corresponds with specific % confidence, find the Z value for the confidence % then: D=TE+(Z( ? ?2CP) ½). Project: has a definite beginning and a definite end, hence a finite duration. Characteristics (def of purpose, project, life cycle, interdependencies, uniqueness, conflict) Purpose-a one time activity with well defined desired end results. Series of jobs for goal takes time. Life cycle- projects evolve in steps -->from a slow beginning they progress to a buildup of size then peak begin to decline then then must die. Interdependencies-projects can interact with other projects within the same parent organization & most typically with the functional departments (marketing, finance ect.) of teh firm. Conflict- projects vs. functional department & project vs prject with respect to resources and personel. Project management: planning directing, and controlling resources (ppl, materials, equipment) to meet the technical, cost, and time constraints of a project. Pure project: self contained team works full time on the project. (morotola razr) Functional project: team members are assigned from the functional depts of an organization. Matrix project blends properties of functional and pure project structures. The project manager decides what tasks and when they will be performed, but the functional managers control which ppl and technologies are used. If this form is chosen, different projects (rows of the matrix) borrow resources from functional areas (colums). Project objectives: Performance (scope. measured based on initial expectations as well), Cost, Time. Project Manager Resp to parent org, the client, project team. Challenges: selecting and motivating personnel, dealing with obstacles, making project goal trade-offs, communicating with all parties, dealing with project risk and potential failure. Inputs into Proj. Scheduling (usually presented as work breakdown structure (WBS) and precedence tables): list of proj. tasks, subtasks, work packages, and activities. Sequence of activities. Activity duration. Resources and their availability. A project starts out as a statement of work (SOW). The SOW may be a written description of the objectives to be achieved, with a brief statement of the work to be done and a proposed schedule specifying the start and completion dates. It also could contain performance measures in terms of budget and completion steps (milestones) and the written reports to be supplied. A task is a further subdivision of a project. It is usually not longer than several months in duration and is performed by one group or organization. A subtask may be used if needed to further subdivide the project into more meaningful pieces. A work package is a group of activities combined to be assignable to a single organizational unit. Completion of one or more work packages results in the completion of a subtask; completion of one or more subtasks results in the completion of a task; and, finally, the completion of all tasks is required to complete the project. Activities are defined within the context of the work breakdown structure and are pieces of work that consume time. Activities do not necessarily require the expenditure of effort by people,lthough often do. For ex., waiting for paint to dry may be an activity in a project. Outputs: Gantt charts. Network diagrams. Gantt chart (bar chart) shows both the amt of time involved and the sequence in which activities can be performed. Two best known network planning models: the Critical Path Method (CPM) & Program Evaluation and Review Technique (PERT) developed to handle uncertain time estimates. TOC: the constraint of a project is the Critical Chain-sequence of dependent events that prevent the project from completing in a shorter time interval. CC incorporates both, resource dependence and duration. When there are no resource constraints, the CC will be your CP. Impact of Human Nature: Parkinson?s Law-work expands to fill the time allowed. 3 Minute Egg Rule-it?s not quality if a task is finished before the time is up. Student Syndrome-always wait to the last minute to start a task. Use Aggressive but Possible Times (ABPT). /// Managing resources- project mgmt info systems- To resolve overallocations manually, you either add resources or reschedule. Mid- to high level project mgmt software info systems (PMIS) software can resolve overalocations through a ?leveling ??feature. Variability on individual paths gets amplified at path-merging nodes. SO, protect the critical path by placing an aggregated buffer on each path that feeds the critical chain. Use Aggressive but Possible Times (ABPT) for task durations . Use smart Buffer Management based on Project and Feeding Buffers . Eliminate dues dates and project milestones, with the exception of final project due date use buffers instead. Any delay in any path can delay the project even if not on CP. Delays are cumulative, but saved time is lost bc have to wait. Many organizations undertake multiple projects simultaneously These projects share resources and personnel and, often, capacity is a constraint. -Avoid multitasking. -Don?t release projects as soon as soon as possible, when there is a capacity constraint. Other standard reports can be used for a more detailed presentation comparing cost to progress (CSSR) or reports providing the basis for partial payment (earned value report) Critial path meathod was developed for scheduling maintence shutdowns (when invented) it is based on assumption that project activity can be guessed accurately & dont vary. PERT was developed to handle uncertain time estimates. Although ghantt chart is able to time in a useable fashion for small projets, the interrelationship of activities become extremely difficult to visualize and to work with for projectrs that include more than 25 activities. Also gantt chart procides no direct procedure for determining the critical path. Probability calcs distinguishing of ERT. Estimated time is calc by using weighted avg of min, max & mose likely. Estimates of variability can estimate project completion time. A tracking gantt- superimposes the current schedule onto a baseline plan so deviations are easily noticed. Deviations btw planned start/finish also appear and a ?slipping filter? can be applied to highlight onlythose tasks that are schdeuled to finish at a later date than the planned baseline. Critical chain- toc to the rescue, any system must have a constraint, the constraing of a project is the critical chain, sequence of dependent events that prevents the project from completin in a shorter time intercal, task and resource dependencies determine the critical chain. Critical path- sequence of activities in a project that forms the longest chain in terms of their time to complete. This path contains zero slack time. ?that happens when there are no constraints? Critical path method steps 1. Identify each activity to be done in the project and estimate how long it will take to complete each. 2. Determine the required sequence of activities and construct a network reflecting the precedence relationships. (identify immediate predecessors-the activities that need to be completed immediately before an activity) 3. determine the critical path. 4. Determine the early start/early finish and late start/late finish. The difference between the late sstart time and early start time is the slack time. (left bottom and left top nums in the box) Early slart schedule- lists all activities by their early start times.Late start sch- lists the activities to start as late as possible w/o delaying completion date. Steps in the development of Network- 1. Activity identification. 2. Activity sequencing and network construction 3. Determine critical path.Slack Time A(1) -> B(2) C(1) (top and bottom each goes to) D(1). So ES EF for A(1) is 0,1 B(2) 1,3 C(1) 1,2 D(1) 3,4. For LS, LF you go backwards like D(1)?s finish is 4 and it takes 1 so C must be done by time 3 so that D can start on time. So LS,LF for A(1) 0,1 B(2) 1,3 C(1) 2,3 D(1) 3,4. Only C has slack bc its not on critical path. Activity direct costs- costs associated with expediting activities and add to projects direct cost. (ex overtime, hiring more ppl, buying more or less equiptment)Project indirect costs- costs associate with sustaining the project (ex. Overhead, facilities, penality costs, opportunity costs ect.) // Because activity direct and project indirect costs are opposing, goal of minimum cost scheduling is to findthe optimum trade off of time and money. To find this point do these 5 steps. 1. prepare a CPM-type network diagram. (must have NC NT CT & CC) 2. Determine the cost per unit of time to expedite each activity (slope of line where CC, CT is a pt connected to NC, NT. Formula for slope = (CC-NC)/(NT-CT) 3. Compute critical path. 4. Shorten the critical path at the least cost. 5. Plot project direct, indirect an total-cost curves and find the minimum cost schedule Look at the Gantt chart, there are a couple of questions on it. I remember specifically there was a question asking what the horizontal axis of a Gantt chart represents. I think it's time, that's what I put, but you might want to double check. There was also a question about what is included in a work breakdown structure. Question about characteristics needed in a Project Manager. Question about what the characteristics of a project are. . I believe you also need to know the difference btw Critical Chain and Critical Path, or what Critical Chain is. There are a few questions about slack time, so know exactly what it is, when it happens, and how to calculate it.
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