# ME 388 – Applied Instrumentation Laboratory Design of Experiments (DOE)

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ME 388 – Applied Instrumentation Laboratory Design of Experiments (DOE)

Reference (If you can find it) R.D Moen, T.W. Nolan, L.P. Provost, Improving Quality Through Planned Experimentation, McGraw-Hill, 1991 D.C. Montgomery, Design and Analysis of Experiments, 5 th Edition, Wiley, 2001

Six Sigma (black belt) System for constant improvement Use of statistical tools for process analysis, problem solving and improvement Six Sigma statement by GE: …The central idea behind Six Sigma is that if you can measure how many "defects" you have in a process, you can systematically figure out how to eliminate them and get as close to "zero defects" as possible…

Definition A powerful “statistics-based” experimental methodology that is used to efficiently determine how multiple independent variables affect dependent variables of a system or process.

A properly executed DOE will… Provide the most information With the fewest amount of tests Compared to a sequential “string-of- pearls” type approach

DOE’s are used for 1.Screening experiments 2.To determine Interactions between independent variables 3.Optimization

Motivation Knowledge Optimization Improvement

Steps to use DOE Have some technical knowledge of process or system (assumed here) Have some statistics background (assumed here) Design experiment (and run) Analyze data

Terminology Factor = independent variable Level = a given value or setting for an independent variable (for example, a 2- level experiment involves testing a high and low value for each independent variable)

2 level, 2 factor design (2 2 ) F2F2 - F 1 + - +

2 level, 3 factor design (2 3 ) F2F2 - F 3 + - F 1 + - +

2 level, 4 factor design (2 4 ) F4F4 F2F2 - F 3 + - F 1 + -- + +- +

Fractional Factorial Designs Reduce number of test At the expense of complete data Rely on reasonable judgments and technical knowledge –Assume triple, quadruple and greater interactions are not significant

2 7-3 design

2 7-4 design

Analysis Develop extended test/design matrix “Effects” are assessed for each variable and combination of variables Effects plots can also be generated

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