Task Information: Defining task distributions
In order to define statistical distribution for task duration, cost,
income, and start time you must define low and base values of
duration, cost, income, and start times using appropriate views and
dialog boxes. For example, in order to define statistical distribution
for cost, you should enter low and high estimates of cost using Cost
and Revenue views.
Use Distribution tab of Task information dialog box to define
distribution.
1. Select the Cost, Income, Duration or
Start Time tab.
2. Select the distribution from the Distribution
list. If you select Undefined, the base value will be used for all
iterations.
3. Define the distribution parameters. The Probability Density chart
is automatically updated. You can adjust distribution parameters
using the sliders.
4. If you use a custom or discrete distribution, a grid opens. The
grid will allow you to define points (or intervals for discrete
distributions) and associated with each point (interval)
5. If you select Normal or Lognormal, you must select the Low and
High probability range (P1 and P99, P5 and P95 or P10 and P90).
These are “cut-off” parameters; meaning that duration, cost, or
start time cannot go beyond these values.
• The Probability
Density chart’s colors are consistent with those found in the
Project Summary and Monte Carlo Simulation Results: Duration is
blue, Cost is green, and Start Time is yellow.
• Double-click on the probability density chart to enlarge it.
• To copy the chart to the clipboard or as a JPEG file, right-click
and choose a copy command from the shortcut menu.
In most real
life examples, the type of distribution (triangular, normal, and
lognormal, etc.) may not significantly affect the results of
calculation. Results of project scheduling cannot be accurate with
high precision due to the large systemic errors of estimation in
project management. It is recommended that you assign different
statistical distribution if you have reliable historical data about
similar tasks. |
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