Los modelos de redes se aplican a numerosos casos en la Ciencia de la Administración , en particular relacionados con la operación de redes de transporte, logística, redes eléctricas o de co…Descripción completa
PEDFull description
pert dan CPMDeskripsi lengkap
trabajo de pert cpm donde se encuentran ejercicios resueltos de dicho temaDescripción completa
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pert dan CPM
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Project management- Network Techniques
DIFFERENCE BETWEEN PERT & CPM
DIFFERENCE PERT
CPM
• PERT (Programme Evaluation & Review Technique) is event oriented.
• CPM (Critical Path Method) is activity oriented.
• PERT activities are shown as a network of precedence relationships using activity-onarrow network construction • PERT treats activity time as a random variable • PERT focuses exclusively on the time variable
• CPM activities are shown as a network of precedence relationships using activityon-node network construction • CPM requires a single deterministic time value for each activity. • CPM includes the analysis
PERT is a probabilistic • PERT Model. It uses three estimates of the activity time- optimistic, pessimistic and most Likely with a view to take into account time uncertainty. • PERT is primarily concerned with time. It helps the manager to schedule and co-ordinate various activities so that the project can be completed on schedule time.
CPM
• CPM is a deterministic model i.e. it dose not take into account the uncertainties. Involved in the estimation of time for execution of a job or an activity. It completely Ignores the probabilistic element of the problem. • CPM place dual emphasis on time and cost and evaluate the trade off between project Cost and project time.
PERT
• Suitable projects
for
CPM repetitive
critical • Demarcate noncritical activities
and
• Suitable for new projects • Does not demarcate between critical and & noncritical activities
• determined on the basis of • Critical path is determined slack on the basis of float • Suitable for defense • Dummies are not required
for • Suitable project settings
• Crashing is not applicable
• Dummies are compulsory
industrial
• Crashing is applicable
CPM analysis • Draw the CPM network • Analyze the paths through the network • Determine the float for each activity – Compute the activity’s float float = LS - ES = LF - EF
– Float is the maximum amount of time that this activity can be delay in its completion before it becomes a critical activity, i.e., delays completion of the project • Find the critical path is that the sequence of activities and events where there is no “slack” i.e.. Zero slack – Longest path through a network • Find the project duration is minimum project completion time
CPM Example • Critical Path
f, 15
h, 9
g, 17
a, 6
i, 6
b, 8 d, 13
c, 5 e, 9
j, 12
PERT • PERT is based on the assumption that an activity’s duration follows a probability distribution instead of being a single value • Three time estimates are required to compute the parameters of an activity’s duration distribution: – pessimistic time (tp ) - the time the activity would take if things did not go well – most likely time (tm ) - the consensus best estimate of the activity’s duration – optimistic time (to ) - the time the activity would take if things did go well Mean (expected time):
t e
=
tp + 4 tm + to 6 2
t
t
PERT analysis • Draw the network. • Analyze the paths through the network and find the critical path. • The length of the critical path is the mean of the project duration probability distribution which is assumed to be normal • The standard deviation of the project duration probability distribution is computed by adding the variances of the critical activities (all of the activities that make up the critical path) and taking the square root of that sum • Probability computations can now be made using the normal distribution table.
Probability computation Determine probability that project is completed within specified time x-
