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Logistics Impact Model – Software Factory 2015
5.5.2. Probability distribution
The beginning of the Event section briefly discussed the probability distribution of events. In this
section, the probability distribution is discussed in detail.
The figure above shows the details of the Detailed shipping information requested-sub event. This
sub event uses normal probability distribution to check whether the sub event is executed or not.
The figure below is a graphical representation of a normal probability distribution with a lower bound
of 55, upper bound of 75, mean of 70 and a standard deviation of 8.9. The dark area is the
acceptance area, when the calculated value is in this area, the event is executed.
Just like Microsoft Excel, LIMO calculates the cumulative value of the upper bound and subtracts the
cumulative value of the lower bound. The following example shows how the normal probability
distribution can be calculated in Microsoft Excel.
Let UB (Upper bound) equal NORM.DIST(75;70;8,9;1)
Let LB (Lower bound) equal NORM.DIST(55;70;8,9;1)
𝑃𝑟𝑜𝑏𝑎𝑏𝑖𝑙𝑖𝑡𝑦 = 100 ∗ (𝑈𝐵 − 𝐿𝐵) = 66.69 𝑝𝑒𝑟𝑐𝑒𝑛𝑡
This will mean that the Detailed shipping information requested-event is executed 66.69 percent of
the time. The chance that the event is executed can be increased or lowered by changing the values
of the normal probability distribution. If the upper- and lower bound are closer to the mean, the
event will be executed less often.
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