Industrial Statistics: Practical Methods and Guidance for Improved Performance

283 Pages·2010·1.23 MB·English

by  Anand M. Joglekar

INDUSTRIAL STATISTICS

INDUSTRIAL STATISTICS
Practical Methods and Guidance for
Improved Performance
ANAND M. JOGLEKAR
Joglekar Associates
Plymouth, Minnesota
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LibraryofCongressCataloging-in-PublicationData:
Joglekar,AnandM.
Industrialstatistics:practicalmethodsandguidanceforimproved
performance/AnandM.Joglekar.
p.cm.
Includesbibliographyreferencesandindex.
ISBN978-0-470-49716-6(cloth)
1. Processcontrol–Satisticalmethods.2. Qualitycontrol–Statistical
methods.3.Experimentaldesign.I. Title.
TS156.8.J622010
658.5072’7–dc22
2009034001
PrintedintheUnitedStatesofAmerica
10 9 8 7 6 5 4 3 2 1
To thememoryof myparents
andto Chhayaand Arvind
Thefollowingage-oldadvicedealswithrobustdesignandcontinuousimprovement
atthepersonallevel.
Youhavecontroloveryouractions,butnotontheirfruits.
Youshouldneverengageinactionforthesakeofreward,
norshouldyoulongforinaction.
Performactionsinthisworldabandoningattachments
andalikeinsuccessorfailure,
foryogaisperfectevennessofmind.
–BhagavadGita2.47–48
MahatmaGandhiencapsulatesthecentralmessageofGitainonephrase:nishkama
karma,selflessaction,workfreefromselfishdesires.Desireisthefueloflife;without
desirenothingcanbeachieved.Kama,inthiscontext,isselfishdesire,thecompulsive
cravingforpersonalsatisfactionatanycost.Nishkamaisselflessdesire.Karmameans
action.Gitacounsels—workhardintheworldwithoutanyselfishattachmentandwith
evennessofmind.
Mahatma Gandhi explains—By detachment I mean that you must not worry
whether the desired result follows from your action or not, so long as your motive
ispure,yourmeanscorrect.Itmeansthatthingswillcomerightintheendifyoutake
careofthemeans.Butrenunciationoffruitinnowaymeansindifferencetoresults.In
regardtoeveryactiononemustknowtheresultthatisexpectedtofollow,themeans
theretoandthecapacityforit.Hewho,beingsoequipped,iswithoutselfishdesirefor
theresultandisyetwhollyengrossedintheduefulfillmentofthetaskbeforehim,is
saidtohaverenouncedthefruitsofhisaction.Onlyapersonwhoisutterlydetached
andutterlydedicatedisfreetoenjoylife.Renounceandenjoy!
–AdaptedfromBhagavadGitabyEknathEaswaran
CONTENTS
PREFACE xi
1. BASICSTATISTICS: HOW TO REDUCE FINANCIALRISK? 1
1.1. Capital MarketReturns / 2
1.2. Sample Statistics / 5
1.3. PopulationParameters / 9
1.4. ConfidenceIntervals and Sample Sizes / 13
1.5. Correlation / 16
1.6. Portfolio Optimization / 18
1.7. Questions toAsk / 24
2. WHYNOT TODO THE USUAL t-TEST AND WHATTO
REPLACE ITWITH? 27
2.1. What isat-Test and what isWrong with It? / 29
2.2. ConfidenceInterval isBetter Than at-Test / 32
2.3. HowMuch Data toCollect? / 35
2.4. Reducing Sample Size / 39
2.5. Paired Comparison / 41
2.6. Comparing TwoStandard Deviations / 44
vii
viii CONTENTS
2.7. Recommended Design and AnalysisProcedure / 46
2.8. Questions toAsk / 46
3. DESIGN OFEXPERIMENTS: ISIT NOT GOING TO COST
TOO MUCHANDTAKE TOO LONG? 48
3.1. Why Design Experiments? / 49
3.2. Factorial Designs / 53
3.3. SuccessFactors / 59
3.4. Fractional Factorial Designs / 63
3.5. Plackett–Burman Designs / 66
3.6. Applications / 67
3.7. Optimization Designs / 71
3.8. Questions toAsk / 75
4. WHATIS THE KEY TODESIGNING ROBUST PRODUCTS
AND PROCESSES? 77
4.1. The Keyto Robustness / 78
4.2. Robust Design Method / 83
4.3. Signal-to-Noise Ratios / 87
4.4. Achieving Additivity / 89
4.5. AlternateAnalysis Procedure / 92
4.6. Implications for R&D / 98
4.7. Questions toAsk / 100
5. SETTING SPECIFICATIONS: ARBITRARY ORIS THERE
A METHOD TO IT? 101
5.1. Understanding Specifications / 103
5.2. EmpiricalApproach / 106
5.3. FunctionalApproach / 107
5.4. MinimumLife Cycle Cost Approach / 114
5.5. Questions toAsk / 119
6. HOW TO DESIGN PRACTICAL ACCEPTANCESAMPLING
PLANSAND PROCESS VALIDATION STUDIES? 121
6.1. Single-Sample Attribute Plans / 123
6.2. Selecting AQLand RQL / 129