Advanced Use Cases of the Bootstrap Method in JMP Pro

Copyright © 2010 SAS Institute Inc. All rights reserved.
Advanced Use Cases of
the Bootstrap Feature in
JMP® Pro
Michael Crotty
Research Statistician
JMP Division, SAS Institute

2
Copyright © 2010, SAS Institute Inc. All rights reserved.
Objectives
 Introduce the bootstrap feature in JMP Pro
 Discuss examples of some non-standard use cases
 Examples are meant to be illustrative, but not
necessarily realistic
 Start conversations with users on ways that they are or
hope to be using the bootstrap feature for their problems
 Hope to inspire customers to share their uses of the
bootstrap feature at Discovery 2013

3
Outline
 Introduce the bootstrap feature in JMP
 Bootstrap as an intro stat teaching tool
 Bootstrapping Examples
 Non-standard quantities
 Functions of the output
 Multiple tables in one bootstrap run
 Model from the Fit Curve platform
 Conclusions

4
Introduction to the Bootstrap
 Introduced by Brad Efron in 1979; grown in popularity as
computing power increases
 Resampling technique that allows you to estimate the
variance of statistics, even when analytical expressions
for the variance are difficult to obtain
 You want to know about the population, but all you have
is one sample
 Treat the sample as a population and sample from it with
replacement
 This is called a bootstrap sample
 Repeating this sampling scheme produces bootstrap replication
 For each bootstrap sample, you can calculate the statistic(s) of
interest

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The Bootstrap in JMP
 Possible to do a bootstrap analysis prior to JMP 10
using a script
 “One-click bootstrap” added to JMP Pro in Version 10
 Available in most Analysis platforms
 Takes advantage of the Automatic Recalc feature
 Results can be analyzed in Distribution platform, which
will know to provide Bootstrap Confidence Limits, based
on percentile interval method (Efron & Tibshirani 1993)

6
Bootstrap in an Intro Stat Course
 Allows students to see the effects of sampling variation
without being bogged down with distribution theory
 Bootstrap method does not require distributional
assumptions on your data or sample
 Avoids some of the feeling of introductory statistics
courses being “just a bunch of formulas”
 (As far as I know,) bootstrap is not widely used in
introductory statistics courses

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Non-standard quantities
 By non-standard, I mean statistics for which we don’t
readily have standard errors
 Could be unavailable in JMP
 Could be difficult to obtain analytically
 Example: Adjusted R^2 value in linear regression

8
Functions of output
 Useful for situations where the statistic of interest does
not appear in a JMP report
 Could be a business-defined function of JMP-reported statistics
 Example: defining a function using a bootstrap sample

9
Multiple tables at one time
 “Trick” to use JSL to select multiple tables in a report
and bootstrap them
 Can also be accomplished by setting a random seed prior to
each separate bootstrap analysis for multiple tables in a report
 Example: Fixed scale parameter in lifetime data
rpt["Parametric Estimate - Normal"][NumberColBox("Estimate")] << select;
rpt["Fix Parameter"]["Parametric Estimate - Normal"][NumberColBox("Estimate")] << select;
dtlst = rpt["Parametric Estimate - Normal"][NumberColBox("Estimate")] << Bootstrap(100);

10
Bootstrapping curves
 Similar to the example for functions of output
 We want to use the bootstrap feature to get a sense of
the variability of a curve fit in the new Nonlinear platform
 Example: Fit Curve
-50
0
50
10
15
20
25
30
pop
1800 1850 1900 1950 2000
year
-50
0
50
10
15
20
25
30
pop
1800 1850 1900 1950 2000
year

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Conclusions
 Bootstrap is a powerful new feature with many uses
 Primarily a UI feature, but capability is enhanced when
scripted in JSL
 Allows us to get confidence intervals for statistics,
functions of statistics and curves
 Review objectives:
 Examples are meant to be illustrative, but not necessarily
realistic
 Start conversations with users on ways that they are or hope to
be using the bootstrap feature for their problems
 Hope to inspire customers to share their uses of the bootstrap
feature at Discovery 2013

12
Acknowledgements, References
 JMP Statistical R&D
 Sam Gardner, Clay Barker, Bill Meeker
 Efron, B. “Bootstrap methods: Another look at the
jackknife.” Annals of Statistics, 7(1):1-26, 1979.
 Efron, B. and Tibshirani, R. An Introduction to the
Bootstrap. Chapman and Hall, 1993.
 Stine, R. “Bootstrap Resampling.” Course notes from
ICPSR Blalock Lectures 2003.
http://www-stat.wharton.upenn.edu/~stine/mich/index.html#bootstrap
Questions?

Copyright © 2010 SAS Institute Inc. All rights reserved.
Thank You!
Advanced Use Cases of the Bootstrap Feature in JMP® Pro
Michael Crotty
michael.crotty@sas.com
Research Statistician
JMP Division, SAS Institute

Advanced Use Cases of the Bootstrap Method in JMP Pro

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