Project scheduling Flashcards
What is PERT/CPM project scheduling used for
To answer 1 what is the total time of the project, 2 when the start and finish dates for each activity is, 3 wich activities are critical (must be completed exactly according to schedule) and 4 how long none critical activities can be delayed before they cause an increase in the projects completion time
What is a project network
A model of precedence of activities
What are nodes in a project network
activities
What are arcs in a project network
The precedence relationship between the activities
What is a critical path for a project network
A path consisting of activities with zero slack
How do you calculate the ciritical path if you have a table with different activities the time it takes to perform them and which activity preceeds them
First map them using a project network where each node points to the ones that can be done to preceed them. Then note down the earlyest start time and finishing time for each node based on the ones before them. Afterwords do the same backwards and note down the latest start time and finish time. Subtract latest and earlyest times to get the slack. The critical path is the one where the slack variables are 0.
What is the formula for a projects mean completion time if it is uncertain and follows the beta distribution
(a+4m+b)/6 where a is the optimistic completion time, b is the pessimistic completion time and m is the most likely completion time
In the three-time estimate approach, the critical path is
determined as if the mean times for the activities were
fixed times.
True
What is the mean and variance of the completion time of a promect in the three time estimate approach
It has a normal distribution with mean equal to the sum of the means along the critical path and variance equal to the sum of the variances along the critical path
How do you calculate the probability of a project being finished within a time
First you calculate the variance the time of each activity if you dont have it. If you have a pessimistiv and optimistic forecast you get it by ((P-O)/6)^2. Then you get the project variance by adding the activity variances along the critical path. Then you get the Z value by subtracting the deadline with the minimal time and dividing it by the project standard deviation wich is the square root of the variance. Lastly you look up the probability of getting a lesser z in a p table
What is the difference between PERT abd CPM
Pert deals with uncertainty and CPM does not
If you have the standard deviation of the sum of the activities durration and the the expected durration of the project how do you calculate the Z value of the probability of finishing before x
Z = (x - expected_completion) / stdev
