New Definition (Network Modeling Method) (Better)
Program Evaluation and Review Technique (PERT)—a network analysis technique
used to estimate project duration when there is a high degree of uncertainty about
the individual activity duration estimates. PERT applies the critical path
method (CPM) to a weighted average
duration estimate. This approach was developed about the same time as CPM, in
the late 1950s, and also uses net-work diagrams, which are still sometimes
referred to as PERT charts.
PERT uses probabilistic time
estimates—duration estimates based on using optimistic, most likely, and
pessimistic estimates of activity durations—instead of one specific or discrete
duration estimate, as CPM does. ln other words, PERT uses a three-point
estimate, as described earlier. To use PERT you calculate a weighted average
for the duration estimate of each project activity musing the following
formula:
By using
the PERT weighted average for each activity duration estimate, the total
project duration estimate takes into account the risk or uncertainly in the
individual activity estimates.
Suppose Sue Johnson's project team in the opening
ease used PERT to determine the schedule for the online registration system project.
They would have to collect numbers for the optimistic, most likely, and
pessimistic duration estimates for each project activity. Suppose one of the
activities was to design an input screen for the system. Someone might estimate
that it would take about two weeks or 10 workdays to do this activity. Without
using PERT, the duration estimate for that activity would be 10 workdays. Using
PERT, the project team would also need to estimate the pessimistic and
optimistic times for completing this activity. Suppose an optimistic estimate
is that the input screen can be designed in eight workdays, and a pessimistic
time estimate is 24 workdays. Applying the PERT formula, you get the following:
Instead of using
the most likely duration estimate 10 workdays, the project team would use 12
workdays when doing critical path analysis. These additional two days could
really help the project want in getting die work completed on time.
The main advantage of PERT is that it attempts
to address the risk associated with duration estimates. Since many projects exceed
schedule estimates, PERT may help in developing schedules that are more
realistic. PERT's main disadvantages are that it involves more work than CPM
since it requires several duration estimates, and there are better probabilistic
methods for assessing schedule risk.
(Kathy Schwalbe, Information Technology Project Management, 236-237)
Gantt and milestone charts are basic scheduling tools, exceeded in their basic versions only in simplicity by a to-do Iist. A more complicated method of scheduling actvities and events uses a network model. The model depicts all the interrelated events that must take place for a proiect to be completed. The most widely used network-modeling tool is thc program evaluation and review technique (PERT). It is used to track the planning activities required to complete a large-scale, nonrepetitive project. PERT was originally developed in 1958 by the United States Department of Defense to assist with the Polaris mobile submarine launch project. PERT has the potential to reduce the time and cost required to complete a project because activities can be sequenced efficiently. A scheduling technique such as PERT is useful when certain tasks have to be completed before others if the total project is to be completed on time. ln the small office building example, the site of the building must be specified before the owner can apply for a building permit. (The building commission will grant a permit only after approving a specific location.) The PERT diagram indicates such a necessary sequence of events. PERT is used most often in engineering and construction projects. lt has also been applied to such business problems as marketing campaigns, company relocations, and convention planning. Here we examine the basics of PERT, along with a few advanced considerations.
DuBrin A.J., Essentials of Management, p.197
2-TRIZ
New
Definition (Problem Solving Theory) (Better)
TRIZ is a
unique, rigorous and powerful toolkit which guides engineers to understand and
solve their problems by accessing the immense treasure of past engineering and
scientific knowledge. TRIZ helps us find the surprisingly few relevant and
practical answers to our real problems. This is made simple by the TRIZ summary
of all the conceptual answers to engineering and scientific problems.
TRIZ is the only solution toolkit which exists
so far in the world that offers engineers help beyond brainstorming at the
actual concept -solution locating and solving moments. There are wonderful
toolkits for understanding problems, with analysis processes for capturing the
requirements, analysing the systems, looking at processes and pinpointing
actual causes of problems. There are also many rigorous and useful toolkits for
the time after problem solving has occurred, including processes for selecting
solutions and developing them, with useful ways of evaluating and predicting
costs etc.; but for the actual moment of problem solving - the search and
capture of the right solutions or new concepts- there is only TRIZ. Until TRIZ
the assumption has been that clever engineers and scientists would somehow find
the right answers either individually or collectively by brainstorming and
using their experience and knowledge.
(Karen Gadd,TRIZ for Engineers: Enabling Inventive Problem Solving, p.3)
Previous
Definiton
TRIZ is a
philosophy, a process and a series of tools based primarily on the concept of
resolving contradictions. ENgineering Contradictions are the crux of many
issues seen to date where copromise or trade-off is needed to balance between
an improving versus a worsening characteristic. This is what's happening in
current manufacturing enviroments and we probably are able to live witht it for
now: but as thechnology advances and equipment are being push harder, the
equipment will break or deteriorate further. The manufacturing enviroment
encompasses any kind of industry which uses equiment or tools in their
manufacturing process.
(Yaoh Teong
San, TRIZ- Systematic Innovation in Manuufacturing, pg:3)
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