A computer dealership knows that the lead time for re-ordering their most popular computer system is 4 weeks. Based upon an average demand of 1 unit per day, the dealership wants to model the number of business days it will take to sell 20 systems.
Checking the conditions of the gamma distribution:
These conditions match those of the gamma distribution. (Note that in this example the dealership has made several simplifying assumptions about the conditions. In reality, the total number of computer purchasers is finite, and some might have influenced the purchasing decisions of others.)
The shape parameter is used to specify the r th occurrence of the Poisson event. In this example, you would enter 20 for the shape parameter (5 units per week times 4 weeks). The result is a distribution showing the probability that x number of business days will pass until the 20th system is sold.
Figure 100, Gamma distribution illustrates the gamma distribution.
