Advances in Industrial Split-Plot Experiments: Applications and Recent Developments
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Geoff Vining's current research focuses on industrial split-plot experiments, highlighting significant differences from agricultural practices. He emphasizes how some factors in experiments provide more information resulting in multiple error terms. His work includes extending split-plot structures to mixture component-process factor experiments and developing minimum whole-plot designs. Recognized for his contributions, Vining received the Lloyd Nelson Award and continues to advance methods for better variance estimation and design equivalence in industrial statistics.
Advances in Industrial Split-Plot Experiments: Applications and Recent Developments
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Presentation Transcript
Background • Industrial Split-Plot Experiments • Important in Industry • Significant Differences from Agricultural Split-Plot Experiments • Hot Area in Industrial Statistics since Late 1990s
Background What is a split-plot experiment? • Experimental unit for some subset of factors is an observation unit for another subset of factors • Originated in agriculture
Background Pencil Lead Response: Strength • Z1-Furnace Temp (Hard-to-Change) • X1-Type of Graphite (Easy-to-Change) • X2-Grinding Method (Easy-to-Change)
Background Z1=-1 Z2=1 X1=-1 X2=-1 X1=1 X2=-1 X1=-1 X2=1 X1=1 X2=1 X1=-1 X2=-1 X1=1 X2=-1 X1=-1 X2=1 X1=1 x2=1
Background • Some factors have more experimental units than others • Consequence: Some factors have more information than others • Multiple error terms!
Second Order Designs • Let m be the number of whole plots. • Let ni be the number of subplots within the ith whole plot. • For a balanced design, ni = n for all the whole plots. • Let N be the total number of subplots.
Second Order Designs Model
Second Order Designs The variance matrix for the estimated coefficients is:
My Current Work • Kowalski, Cornell, Vining (Technometrics, 2002) • Extends split-plot structure to mixture component – process factor experiments • Proposes a pure-error basis for estimating variance components • Assumes GLS to estimate the model
My Current Work By accident, discovered a modification of a CCD attained OLS-GLS equivalence Vining, Kowalski, Montgomery (JQT 2005) Balanced Designs Allows Pure Error Estimates of Var Comp Show General Conditions Examples of CCD and Box-Behnken Recently Won the Lloyd Nelson Award
My Current Work OLS-GLS Equivalence is Nice: • Estimates do not depend on the unknown variance components • Estimates are BLUE • Properties of the estimates do not rely on asymptotics
My Current Work OLS-GLS Equivalence if there exists a non-singular matrix F such that
My Current Work • Parker, Kowalski, Vining (submitted to Technometrics) • Extends VKM for the balanced case • Develops “minimum whole plot” designs • QREI (2006) outlines catalog of designs • Parker, Kowalski, Vining (submitted to JQT) • Unbalanced Case
My Current Work • Key to Pete’s Work:
My Current Work A Design is OLS-GLS equivalent if
My Current Work • Vining and Kowalski (submitted to JQT) • Develops exact tests for OLS-GLS equivalent designs • Establishes proper residuals for diagnostic plots
My Current Work • Li Wang (current Ph.D. student) • Box and Hunter (Annals 1957) for split-plot designs • Recommendations for axial runs • “partial rotatability” • Orthogonal Blocking