How to create an experiment design that is robust to a linear time trend in the response

Bradley Jones
Bradley Jones|April 30, 2012

It is fairly common that experiments run in a time sequence experience linear drift in the response over the course of the experiment. If you randomize the order of the runs, then the effect of this drift will not tend to bias the estimated factor effects, but it will increase [...]

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Revised in JMP 10: Power Analysis in Custom Design

Bradley Jones
Bradley Jones|April 9, 2012

In my previous post, I talked about the fundamental quantities that affect the ability of a designed experiment to detect non-negligible effects of the factors. These are: 1)      The size of the effect 2)      The root mean squared error (RMSE) of the fitted model 3)      The significance level of the [...]

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Fundamentals of power analysis in experiment design

Bradley Jones
Bradley Jones|April 2, 2012

When I took my first course in linear models and design of experiments, my professor told the class that the most common question that he encountered in his statistical consulting was, “How many samples do I need [for my results to be statistically significant]?” This question comes out of a [...]

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New in JMP 10 DOE: Simultaneous addition of multiple covariate factors

Bradley Jones
Bradley Jones|March 26, 2012

Among other kinds of factors, the Custom Designer in JMP has a mechanism for adding factors with values that are not controllable but are known in advance of experimentation. I call these factors covariate factors, although in regression analysis covariates have a slightly different meaning. Can you provide a realistic [...]

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New in JMP 10 DOE: Discrete Numeric Factors

Bradley Jones
Bradley Jones|March 19, 2012

Among other kinds of factors, the Custom Designer in JMP has facilities for continuous factors and for categorical factors with an arbitrary number of levels. The designer assumes that continuous factors can take any value within the specified range from low to high. Sometimes, though, there are practical restrictions to [...]

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New in JMP 10 DOE: Pre-specified center runs

Bradley Jones
Bradley Jones|March 12, 2012

When one or more factors in an experiment are continuous, many investigators like to add several runs at the center of the design region. This practice accomplishes two things: 1) It allows for a test of overall curvature. 2) It provides replicated runs, which means that JMP can calculate an [...]

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Mathemagical musings

Bradley Jones
Bradley Jones|March 5, 2012

Take a look at this matrix of symbols. ++++++++++++++++++++++++++++++++ +−+−+−+−+−+−+−+−+−+−+−+−+−+−+−+− ++−−++−−++−−++−−++−−++−−++−−++−− +−−++−−++−−++−−++−−++−−++−−++−−+ ++++−−−−++++−−−−++++−−−−++++−−−− +−+−−+−++−+−−+−++−+−−+−++−+−−+−+ ++−−−−++++−−−−++++−−−−++++−−−−++ +−−+−++−+−−+−++−+−−+−++−+−−+−++− ++++++++−−−−−−−−++++++++−−−−−−−− +−+−+−+−−+−+−+−++−+−+−+−−+−+−+−+ ++−−++−−−−++−−++++−−++−−−−++−−++ +−−++−−+−++−−++−+−−++−−+−++−−++− ++++−−−−−−−−++++++++−−−−−−−−++++ +−+−−+−+−+−++−+−+−+−−+−+−+−++−+− ++−−−−++−−++++−−++−−−−++−−++++−− +−−+−++−−++−+−−++−−+−++−−++−+−−+ ++++++++++++++++−−−−−−−−−−−−−−−− +−+−+−+−+−+−+−+−−+−+−+−+−+−+−+−+ ++−−++−−++−−++−−−−++−−++−−++−−++ +−−++−−++−−++−−+−++−−++−−++−−++− ++++−−−−++++−−−−−−−−++++−−−−++++ +−+−−+−++−+−−+−+−+−++−+−−+−++−+− ++−−−−++++−−−−++−−++++−−−−++++−− +−−+−++−+−−+−++−−++−+−−+−++−+−−+ ++++++++−−−−−−−−−−−−−−−−++++++++ +−+−+−+−−+−+−+−+−+−+−+−++−+−+−+− ++−−++−−−−++−−++−−++−−++++−−++−− +−−++−−+−++−−++−−++−−++−+−−++−−+ ++++−−−−−−−−++++−−−−++++++++−−−− +−+−−+−+−+−++−+−−+−++−+−+−+−−+−+ ++−−−−++−−++++−−−−++++−−++−−−−++ +−−+−++−−++−+−−+−++−+−−++−−+−++− Beautiful isn’t it? This matrix has several wonderful properties. Ignoring [...]

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New in JMP 10 DOE: Individual run replication

Bradley Jones
Bradley Jones|February 27, 2012

Replication is one of the four basic principles of experiment design introduced by R. A. Fisher. The other three were the factorial principle, randomization and blocking. The value of replication is that it provides an estimate of the run-to-run variability in the response that is unaffected if the model is [...]

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What price orthogonality?

Bradley Jones
Bradley Jones|February 20, 2012

On Feb. 8, my colleague, Professor Douglas Montgomery of Arizona State University, and I presented a webinar for the American Statistical Association. Our first demonstration dealt with designing an experiment for six factors each having two levels in 24 runs. One natural way to construct such a design would be to [...]

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New in JMP 10 for experiment design: Evaluate Design

Bradley Jones
Bradley Jones|February 6, 2012

JMP 10 is coming in March. In my next few posts, I plan to share the main new capabilities in the area of experiment design. The most visible of these new features is the Evaluate Design item on the DOE menu. What does the Evaluate Design feature do? Evaluate Design [...]

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