Page 670 - ExtendSim User Guide

P. 670

```
644 Analysis
Blocks that calculate statistics
Queue Statistics model
The Queue Statistics model uses the Statistics block to gather information about queues. This discrete event model is located in the folder \Examples\Discrete Event\Statistics.
Queue Statistics model
Clear Statistics
As discussed in “Non-terminating systems” on page 609, when you start a simu- lation run there is no data in the model. After the model has been running for a while, it gets to the point where it is functioning more like the real system. The interval from when the model starts to when it is functioning in a steady or nor- mal state is called the warm-up period.
The Clear Statistics block (Value library) clears the statistics for selected blocks, eliminating the statistical bias of a warm-up period. The type of blocks include:
• Activities(Activity,ConveyItem,Transport,Workstation) • Exit block
• Mean&Varianceblock
• Queues (Queue, Queue Equation, Queue Matching)
• Resources (Resource Item, Resource Pool) • Information block
• Rate library blocks
The block can reset statistical accumulators at periodic intervals or in response to a system event. The block can be placed anywhere in the model. Choose in its dialog which types of blocks will have their statistics cleared. The Clearing Statistics example, a discrete event model shown on page 297, uses the Clear Statistics block to restart model statistics after 40 seconds.
Mean & Variance
The Mean & Variance block (Value library) calculates the mean, variance, and standard deviation of the values that it receives during a simulation run, based on a specified confidence interval. Settings in the block’s dialog allow you to use time weighted statistics, calculate a moving average for a selected interval, calcu- late the statistics over multiple runs, and more.
How To
```