BestFit 4.5 is the stand-alone distribution fitting component of all editions of the DecisionTools Suite.
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 the choice for professionals everywhere.
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About BestFit
BestFit is a Windows program 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
program 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 modeling 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.
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.
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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!
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 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 modeling 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. When you're 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.
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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 optimize 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:
- For input sample data, parameters are estimated using maximum-likelihood estimators. For density and cumulative data, the method of least squares is used to minimize the distance between the input curve points and the theoretical function.
- Fitted distributions are ranked using one or more fit statistics, including Chi-square, Anderson-Darling, and Komolgorov-Smirnov.
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 programs for further analysis and presentation.
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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, colors,
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).
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.
Customize 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 PDF manual is written in plain, easy-to-understand English. And, Palisade offers ongoing seminars on how to use BestFit to analyze your data for use in @RISK, PrecisionTree, and other models!
Use With Other Palisade Software
BestFit 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 optimization 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 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 Kit. This powerful package allows a development
team to create an application utilizing 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 version.
» Learn more about the BestFit Developer Kit, including examples and free trial