Page 671 - ExtendSim User Guide
P. 671

The dialog provides four methods of capturing statis- tics:
• Entirerun
• Moving average
• Interval
• Multiple runs
There are also two options for how the variance is cal- culated:
• Usenumberofinputstocalculatevariance.Thevari- ance is computed as the sum of (valid inputs - mean)^2  (number of inputs).
• Use number of inputs-1 to calculate variance. The variance is computed as the sum of (valid inputs - mean)^2  (number of inputs - 1).
Analysis 645
Confidence intervals
Mean & Variance dialog
A Quantiles option on the Results tab allows you to see what proportion of the observations fall within an interval.
The Mean & Variance block uses 1/(N-1) as an averaging factor. If an input is a NoValue, it is ignored and does not affect the statistics.
To use this block, connect a value output from of the block of interest to the Mean & Variance block’s input.
The Monte Carlo model, located in the folder \Examples\Continuous\Standard Block Models and discussed on page 49, is an example of using the Mean & Variance block.
Information
The Information block (Item library) reports statistics about the items that pass through it. It is useful for counting the number of items and for determining cycle time statistics and the time between item arrivals (TBI). The block reports the average and the current statistics, as well as the minimum and maximum.
The Information block can only be used in models that use item-based blocks, and it must be connected to a block’s item output. This block is used to calculate cycle time in the section “Cycle timing” on page 312.
Cost Stats
Confidence intervals
Confidence interval estimation tells you, with a given level of probability or confidence, how close the average simulation results are to the model’s true average or mean. The confidence interval is the range within which it is predicted the true mean is located. This is expressed as the probability that the true mean lies within interval x± y, where “x” is the average obtained by multiple observations and “y” defines the outer limits of the interval’s range. The confi-
The Cost Stats block (Item library) records in a table the input costs and total cost generated by each costing block in a model. This block reports cost information for item-based blocks, such as for a discrete event model. Information can be exported to a spreadsheet. The block can be placed anywhere in the model.
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