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Home > Palisade Products > Risk Analysis > BestFit


Fit Your Data to the Best Distribution... in Seconds!

New BestFit 4.5 is the latest release of the world's most popular distribution fitting software! BestFit 4.5 is available as a stand-alone programme or fully integrated with @RISK 4.5. Using advanced fitting algorithms, BestFit finds the distribution curve which best describes your data set. An Office-compatible interface, dazzling graphics, and capacity for larger data sets makes BestFit 4.5 the choice for professionals everywhere.

BestFit's graphic overlays and statistics allow you to easily compare fit results.  
Click to view larger graphic.

"BestFit is a really solid distribution selector, and @RISK is a good backbone for the qualitative and quantitative work I perform. I like the flexibility."
Bruce Siegel, Engineering and Business Process Consultant

About BestFit
BestFit is a Windows programme which finds the distribution that best fits your data. Simply import your data set into BestFit and click the Run Fit button. BestFit tests up to 27 different distribution types to find the best fit for your data. You can display results as presentation-quality graphs, or generate a full statistical report. Automatic goodness of fit testing will show you at a glance the accuracy of BestFit's answers. BestFit 4.5 is available as a stand-alone programme or fully integrated with every copy of @RISK 4.5 Professional and Industrial, the risk analysis and simulation add-in for Excel.

BestFit in Industry
Who should use BestFit? Anyone who works with data can use BestFit. Apply it to business situations such as actuarial or claims adjustment, or to science and engineering problems such as oil well drilling or time between events. You can import data from your spreadsheet and export the results as graphic files to your report or presentation.

So why fit distributions to data? Because if you don't (or if you select the wrong distribution), any analysis you run could have serious errors that can cost you time and money. If your data was generated by a random process, you'll get the best modelling results possible by accurately describing that process. And the best way to do that is with a fitted probability distribution.

Using BestFit
How easy is BestFit to use? There are two basic steps:

Step 1: Bring in Your Data
BestFit can take data in three formats: sample, density, or cumulative. How much data? Up to 100,000 data points! You can have BestFit read in data from a text file, enter data by hand, or cut and paste data from any Windows application. You can fit data from the results of an @RISK 4.5 simulation simply by choosing the Fit command from the Explorer list pop-up menu in the @RISK Results Window.

Do you keep your data in Excel? When using BestFit integrated with @RISK, simply highlight your data set in Excel, right click, and choose Fit Distributions to Data from the pop-up menu. This links your data range directly to BestFit. When the data in your spreadsheet changes, BestFit updates your fits automatically!

Step 2: Click the Run Fit Button
Start fitting using default settings by clicking the Run Fit button on the BestFit toolbar. BestFit tests up to 27 continuous and discrete distributions to determine which distribution best fits your data.

BestFit determines the optimal parameters for each distribution, performing three standard tests to determine the goodness of fit: Chi-squared, Anderson-Darling (A-D) and Kolmogorov-Smirnov (K-S). When BestFit is finished, the distributions fit are listed in order of goodness of fit.

BestFit 4.5's Distribution Palette makes choosing your distributions a snap!
Click to view larger graphic.

View, Edit and Draw Distributions
BestFit features a Distribution Viewing window that allows you to preview and edit 37 different continuous and discrete distribution functions. Not sure what a particular distribution looks like? Just select it from the drop-down menu and instantly see a graph of the distribution. Type in desired parameters or adjust them with spin buttons, and watch the graph update as you change parameter!

New BestFit 4.5 also features a pop-up Distribution Palette with thumbnail pictures of all available distribution types. Just click on the thumbnail you wish to use. Choosing distributions couldn't be easier!
BestFit 4.5 now supports alternate parameters for your distributions. There may be instances where you wish to use a particular distribution function, but you don't have enough information to determine the parameters for that distribution. For example, from experience you may know that a normal distribution best describes the net pay of an oil reservoir, but you don't have enough information about the field to know what the mean and standard deviation of the distribution may be. You can now enter those percentile values directly, giving you even greater modelling flexibility. For example, you can use survey or historical data to estimate the 10th and 90th percentiles of a normal distribution instead of guessing at the mean and standard deviation. You can even use a combination of standard and percentile parameters.

BestFit also features a Distribution Artist to let you draw distribution curves freehand with your mouse. In the absence of data, this is a very powerful feature. Simply enter a minimum and maximum value, then use the mouse to sketch your curve in between. Stretch the curve up or down at any point when you want to change its shape. A smoothing function helps those shaky hands. Done with your newly created masterpiece? BestFit changes your drawn curve to a General function.

BestFit can also calculate the standard distribution type and parameter values that "fit" your curve the best! All you have to do is click the Fit Curve button in the BestFit toolbar and use the resulting distribution function in your model!

BestFit Features

Fits to sample, density, or cumulative data
Takes data from text files, other Windows applications, Excel, or @RISK
Input up to 100,000 data points or pairs
Direct link to spreadsheet data in Microsoft Excel for automatic updating of fits
Direct link to @RISK functions for automatic updating
Filtering to remove outliers from data
Fits to 27 available distribution functions
Parameter selection using maximum-likelihood estimators and method of least squares
Uses three goodness of fit tests: Chi-square, Anderson-Darling, and Komolgorov-Smirnov
Complete statistics report, including goodness of fit, confidence levels, percentile and target values

Presentation-quality graphs displayed in BestFit or transferred automatically to Excel's native format
Sliding delimiters on all graphs make finding probabilities and target values easy
Ability to have multiple data sets and fits in a single project
Fit to custom list of predefined distributions you specify
Full control over Chi-square calculations
Preview and edit distributions
Distribution Palette gallery of Distributions
Alternate percentile parameters for distributions
Draw distributions freehand and fit them to standard distributions
On-line Help with "How Do I?" interface

BestFit fits to standard distribution types or predefined distributions you enter.  
Click to view larger graphic.

Distribution List

Error Function
Extreme Value
Inverse Gaussian
Negative Binomial
Pearson Type V
Pearson Type VI
Student's t

How BestFit works
BestFit's goal is to find the distribution that best fits your input data. BestFit does not produce an absolute answer, it identifies a distribution that most likely produced your data.

For a given distribution, BestFit looks for the parameters of the function that optimise the goodness of fit, a measurement of the probability that the input data was produced by the given distribution. Always evaluate your BestFit results quantitatively and qualitatively, examining both the comparison graphs and statistics before using a result.

BestFit goes through the following steps when finding the best fit for your input data:

BestFit gives you all the information you need to decide which fit is the best, and whether that fit is good enough to use. All results, including graphs, statistics and distribution functions, can easily be transferred to other programmes for further analysis and presentation.

BestFit gives you multiple graphing options and full statistics for your fits.  
Click to view larger graphic.

Stunning Graphs
High resolution graphics are used to present the results from your BestFit run. Comparison, Difference, Probability-Probability (P-P) and Quantile-Quantile (Q?Q) graphs are all available. All graphs feature sliding delimiters to easily view specific probabilities or axis values. Want to compare a probability value for your input data and a fitted distribution? Simply slide the delimiter on the graph and see the calculated probabilities both on the graph and in the linked statistical report. Graph types and formatting can be quickly changed using toolbar icons, and rescaling is done by dragging axis limits directly on your graph. Change titles, colours, and more! All graphs can be displayed in Excel for further enhancement and hard copy. With BestFit, it's easy to clearly and effectively communicate complex results to others.

Detailed Statistics and Goodness of Fit Reports
BestFit generates full statistics and goodness of fit data for your fits in convenient tabbed reports linked to the active graph. Detailed statistics such as mean, variance, skewness, kurtosis and more are reported for the input data and resulting distribution. In addition, BestFit gives you access to full goodness of fit results for all three statistical tests (Chi-Square, A-D, and K-S). BestFit results are used with @RISK 4.5 Professional and Industrial for Excel, and can also be used with @RISK for Project and RISKOptimizer. With BestFit 4.5, all your simulations can take into account real-world data, giving you more accurate results!

Fit Summary Gives you Critical Values, Target Values and More!
In addition to the Statistics and Goodness of Fit tabs, BestFit can generate a comprehensive Fit Summary report. This report gives you, in convenient spreadsheet format, formulas, parameters, full statistics, and goodness of fit data for all fitted distribution functions. Plus, it displays Target Values and Critical Values for each distribution tested. Target Values tell you the probability of achieving a specific outcome, and Critical Values identify the criteria by which BestFit accepts or rejects a fit. These Critical Values can be used to determine how good a fit BestFit has found.

Customise Your Fits
Want to have more control over BestFit? You can tell BestFit which distributions you want it to try. BestFit also gives you full control over Chi-squared calculations, including equal interval binning, equal probability binning, and full custom binning. Furthermore, you can select predefined distributions with preset parameter values to fit. By giving you access to all these controls, BestFit allows you to tailor your fits to more precisely meet your needs. However, if you don't use all these features, BestFit will run fits automatically for you!

Get Up to Speed Fast!
BestFit comes with a complete on-line help system that uses an intuitive "How Do I?" interface. Simply type in what you want to do, or search the comprehensive index. Furthermore, the BestFit manual is written in plain, easy-to-understand English. If you would like further resources, Palisade carries a number of excellent titles on statistical fitting, including Risk Analysis: A Quantitative Guide, Simulation Modeling and Analysis and Statistical Distributions. And, Palisade offers ongoing seminars on how to use BestFit to analyse your data for use in @RISK, PrecisionTree, and other models! Visit www.palisade-europe.com for the latest schedule.

Use With Other Palisade Software
BestFit was designed to work with our other DecisionTools Suite products - TopRank®, RISKview™, @RISK and PrecisionTree®. Start by using TopRank, the What-If Analysis add-in for Excel, to identify the critical values in your model. Next, in @RISK, the Risk Analysis and Simulation add-in for Excel, describe your uncertain values using probability distribution functions. Use RISKview to preview distributions or create one by simply drawing it and placing it directly in @RISK. Take real-world data and use BestFit to find the distribution which best fits your data, and use that function in @RISK to realistically represent uncertainty. Then run a thorough Monte Carlo simulation and analyse the results! Create a decision tree with PrecisionTree to accurately describe a decision, and use @RISK to perform a Monte Carlo simulation on your decision tree! With the DecisionTools Suite, you will be prepared to face the risks in any situation!

BestFit also works with RISKOptimizer™ and @RISK for Project. Use BestFit to find the best distribution for your data sets, and insert that distribution right in your Project or RISKOptimizer models! Then run a Monte Carlo simulation on your Project schedule with @RISK for Project, or run an optimisation in Excel combined with Monte Carlo simulation with RISKOptimizer! One copy of BestFit is all you need to find accurate, reliable distributions to describe your uncertainty in any model!

BestFit Developer’s Kit Available
In addition to using BestFit with other Palisade applications, many companies wish to use BestFit within their own applications. As a solution, we provide the BestFit Developer’s Kit. This powerful package allows a development team to create an application utilising BestFit’s various technologies, enabling you to escape the bounds of Excel and use our functionality in your own software. View examples and download a free trial.

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BestFit System Requirements
Minimum Platform: IBM PC compatible Pentium-equivalent or higher, 16MB RAM, Windows 98, NT 4.0, Windows 2000, Windows XP
Recommended: 32 MB RAM, or greater
Version: 4.5
Developer's Kit : BestFit Developer's Kit
Technical Support: 30 days free. Further support available through Maintenance Plan.
Demo: Web download and free demo CD with trial version available.
Training: Available through Palisade's Software Training Courses.