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Crystal Ball is a Monte Carlo simulation add-in to Microsoft Excel, from Oracle.

### Crystal Ball 5.5

At the time ModelAssist was developed for Crystal Ball, Crystal Ball version 5.5 was used and only in a few example models Crystal Ball version 7.0 was used (see for a list below), because it offered a few extra capabilities. However, in the new version of ModelAssist, with the improvements in Crystal Ball version 11.1.2, all the models were updated accordingly. The software is designed in such a way that all of the content of ModelAssist for Crystal Ball is valid and applicable to all versions. In addition, because ModelAssist is mainly focused on risk analysis concepts, methods and techniques, it will also prove useful for users of earlier versions of Crystal Ball.

### Crystal Ball 7.0

Crystal Ball 7.0 included a range of improvements and enhancements compared to Crystal Ball 5.5. Below are highlighted two areas of the improvements that we, at EpiX Analytics, believe are particularly useful:

I. New distributions

In Crystal Ball 7.0, there are four new distributions available in the distribution gallery:

1 .Student's t-distribution:

This distribution is discussed here;

2. Yes/No distribution:

This is another name for the Bernoulli distribution. In Crystal Ball 5.5-, a Yes/No distribution was normally constructed by a using a Binomial(p,1) distribution.

3. Discrete Uniform distribution:

Crystal Ball's Discrete Uniform distribution models an Integer Uniform distribution, which is a special case of the more general Discrete Uniform distribution that can be constructed with Crystal Ball's Custom Distribution. Both methods to construct a Discrete Uniform distribution are illustrated with an example here. The Discrete Uniform distribution can also be seen as a Discrete form of the Uniform distribution.

4. Minimum Extreme distribution:

The MinimumExtreme value distribution is a negatively skewed distribution often use to describe the smallest value of a certain distribution. In Crystal Ball 5.5-, the Minimum Extreme value distribution can be constructed from the Extreme value distribution by reversion the sign of x (as explained in this section).

In addition, the Beta distribution in Crystal Ball 7.0+ has four input parameters, which makes it a general form of the three-parameter Beta that was present in Crystal Ball 5.5-. Both Beta distributions are related to each other as follows:

Four-parameter Beta (Min,Max,a,b) = Min + {Three-parameter Beta (a,b,(Max-Min))}, as is also described here.

II. Custom Distribution

We believe the greatest improvement in Crystal Ball 7.0 is that it allows you to link Crystal Ball's Custom Distribution with input data in your spreadsheet. In other words, a change to your Custom Distribution input data on your spreadsheet will automatically result in a change to the shape of the Custom distribution. This is useful in the following two situations:

1. If you change data on your spreadsheet this will result in a change in the Custom Distribution (this not the case in Crystal Ball 5.5-).

2. A change to the input of the Custom Distribution during a simulation (for example because the input of the distribution is variable or uncertain) will also result in a change to the Custom Distribution (the latter is called "dynamic referencing").

You can link data in your spreadsheet with the Custom Distribution in Crystal Ball 7.0 by using the "Load data" option when defining a Custom Distribution, and selecting the "Keep linked to spreadsheet" option as is shown. This is a very useful improvement to Crystal Ball and we highly recommend that you always select the "keep linked to spreadsheet" option. In fact, the following models use this feature as they require "dynamic referencing":

Especially because of the capability of Crystal Ball 7.0 to link the Custom Distribution to its input in your spreadsheet, we prefer this version of Crystal Ball above earlier versions.

### Crystal Ball 7.1

The main improvement of Crystal Ball version 7.1 compared to earlier versions is it provides the possibility to run model with "extreme speed", e.g. up to 100 times faster than previous versions. We discuss the main advantages of this in a special section about the Extreme Speed feature.

### Crystal Ball 11.1.2

With the purchase of Crystal Ball by Oracle in year 2007, the numbering of the versions changed to be in line with the other Oracle products, that is why there is a jump from version 7 to version 11. There has been a few changes in the new version which we believe are not major, but are implemented and updated in the new version of ModelAssist. The most important one is the removal of the Extreme Speed feature.

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