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Improved Add-In for confidence limits for combinations of variance components in Mixed Models (2020-US-30MP-623)

Level: Intermediate

 

Hadley Myers, JMP Systems Engineer, SAS
Chris Gotwalt, JMP Director of Statistical Research and Development, SAS

 

The need to determine confidence intervals for linear combinations of random mixed-model variance components, especially critical in Pharmaceutical and Life Science applications, was addressed with the creation of a JMP Add-In, demonstrated at the JMP Discovery Summit Europe 2020 and available at the JMP User Community. The add-in used parametric bootstrapping of the sample variance components to generate a table of simulated values and calculated “bias-corrected” (BC) percentile intervals on those values. BC percentile intervals are better in accounting for asymmetry in simulated distributions than standard percentile intervals, and a simulation study using a sample data set at the time showed closer-to-true α-values with the former. This work reports on the release of Version 2 of the Add-In, which calculates both sets of confidence intervals (standard and BC percentiles), as well as a third set, the “bias-corrected and accelerated” confidence interval, which has the advantage of adjusting for underlying higher-order effects. Users will therefore have the flexibility to decide for themselves the appropriate method for their data. The new version of the Add-In will be demonstrated, and an overview of the advantages/disadvantages of each method will be addressed.

 

 

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Speaker

Transcript

Hello, my name is Chris Gotwalt
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has been developed for variance
components models, we we think
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statistical process control
program, one has to understand
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ascertain how much measurement
error is attributable to testing
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there might be five or 10 units
or parts tested per operator,
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different measuring tools is
small enough that differences in
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measurement to measurement,
repeatability variation, or
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measurement systems analyses, as
well as a confidence interval on
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interval estimates in the report
and obtain a valid 95% interval
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calculate confidence intervals,
because we believed it would be
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and the sum of the variance
components. Unfortunately, the
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r&r study. So because variance
components explicitly violate
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you were to use the one click
bootstrap on variance components
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less. So when we were designing
fit mixed, and the REML
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independent. So back to the
drawing board. So it turns out
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in JMP. One approach is called
the parametric bootstrap that
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comparison of the two kind of
families of bootstrap. So the
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they're, they're not assuming
any underlying model. And it's
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the rows in the data table are
independent from one another.
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values, it has the advantage
that we don't have to make this
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bootstrap simulation. The
downside to this is that you
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do a quick introduction to what
the bootstrap...the parametric
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to identify or wanted to
estimate the crossing time of a
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162.8. Now, we want to use a
parametric bootstrap to to go
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has the ability to save the
simulation formula back to the
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that uses the estimates in the
report as inputs into a random
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And we take our estimates and
pull them out into a separate
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And then what we have can be
seen as a random sample from the
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formula column for the crossing
time. And that is automatically
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those...on the crossing time, or
any quantity of interest. When
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simulation, create a formula
column of whatever function of
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derive quantity of interest and
obtain confidence intervals
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the add in so that you're able
to do this quite easily for
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we'll start by showing you how
to run the add in yourself once
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first version was presented at
the JMP 2020 Discovery Summit
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overview, but we'll show you the
references where you can dive in
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perfectly fine as well. So I'm
going to go ahead and start with
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makes use of the fit mixed
platform, right, created from
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the add in will only work with
JMP Pro. So someone might,
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want some measure like
reproducibility. So that would
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as we said, to calculate the
estimate for these, there's no
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columns here. The reality is
much, much, much more
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of the estimate without
considering the worst case
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production that the actual
variance is higher than they have
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don't risk being out of spec in
production. So to run the add in
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From here, I can select the
linear combination of confidence
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simulations, you get a better
estimate of the confidence
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2500. I'm going to leave it as
1000 here just for demonstration
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operator or the batch variable,
and then press perform analysis.
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purpose of this demonstration, I
think I will stop it early.
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calculated confidence limits, the
bootstrap quantiles, which are
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these two tabs. But if you'd
like to see how those compare,
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so what does enough mean, enough
for your confidence limits to
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stopped it before a thousand. So
that's how the add in works. And
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distributed around the original
estimate, they are in fact
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relaunch this analysis. So
you'll see that when the
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European Discovery, required
bounded variance confidence
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that, if that happens for some
of the bootstrap samples or for
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early, again, I'll just let it
run a little bit. Yeah, so I, as
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the samples are allowed, in some
cases, to be below zero. So in
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simulation column here, this
column of simulated
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see them both at the same time.
It's a bit... it's a bit tricky,
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right components, it's a good
idea to run the add in directly
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that column is then deleted. So
one thing to to mention, before
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accounts for the skewness of the
bootstrap distributions, right,
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that. And then the accelerated
takes that even further. So here
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thing to mention is that the
alpha in this represents the
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value for which it's been
calculated? And what can we do to
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up to investigate the four
different kinds of the variance
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method, the bias corrected
method and the BCa. We also
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study. So for all 16
combinations of these three
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combinations of confidence
intervals, and kept track of how
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coverage as we're varying these
three variables, and we see here
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techniques. And the second best
is the bias corrected and
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the best one. Now, if you turn
no bounds on, which means that
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variance components with a
pretty close to 95% coverage.
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intervals are performing
similarly at about 93%. But
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to what a master's thesis paper's
research would have, would
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potentially more work to be
done. There's other interval
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things like generalized
confidence intervals. General
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intervals might also do the
trick for us as well. Hadley's
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so that you can now do
parametric bootstrap simulations
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16. When you bring that up, you
can enter the linear combination
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