By Hervé Thiriez
BestFit is a program which finds the distribution that best fits your data. For a given distribution, BestFit calculates the parameters optimizing the goodness-of-fit. This program also works in relation with spreadsheets (Excel or Lotus 1-2-3).
With the SETUP program provided on disk, there is no problem with the installation. When you use a spreadsheet program, BestFit is installed in the list of add-ins and its icon is added to the toolbar.
The Input Data
The input data may be of three kinds: sample data (a set of values chosen from a population), density data (value and probability pairs) and cumulative data (the same principle, but the probability values correspond to cumulative probabilities). You may enter data directly into BestFit, but the most efficient approach is to link BestFit to data already present in your spreadsheet: this is very simple, all you have to do is to select the data in the sheet, and click on the BestFit icon; BestFit will then open with a link to the selected data. You may also copy data in the spreadsheet and link-paste them into BestFit.
One of the three disks provided with the software is a tutorial disk. The tutorial is directly accessible in the Help menu and includes a nice feature: the tutorial files are packed in order to save disk space and it is possible, by answer to a prompt when starting it, to choose between a temporary unpacking of the tutorial files or a permanent one.
When you start the program, the menu bar and the toolbar appear on the screen: the tools are efficient for giving you a fast access to the main commands. Most of the commands of BestFit may be accessed directly through the toolbar. The first four tools are standard and require no specific explanation.
The following four tools are the major BestFit tools with AutoFit, which runs the automatic fitting procedure, Wizard, if you want to choose your own fitting parameters, Results, which lists the results window, and Statswhich calculates and shows a screen with detailed statistics, both on the input series and on each of the possible distributions.
The last tools respectively start the On-Line Help, run the edit commands (Cut, Copy and Paste are only listed when it has meaning), and RISKview provides direct access to another Palisade product.
RISKview, accessible through the last tool in the toolbar, is a distribution viewing companion to @RISK and BestFit: RISKview helps you select a distribution function for use in @RISK by previewing different distributions and parameters before introducing them to your model. It also includes a "Distribution Artist", a tool which extracts data points from a probability curve that you draw.
There is a network version of BestFit which allows you to use the program on a server-based PC network. To the user, the system will function exactly as it does in its single user version. However, you do need the network version if you want to avoid access conflicts and other problems.
Our overall impression is excellent: BestFit is really easy to use. The tutorial is a reliable introduction to the software and, with the on-line help, should answer most questions.