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RELIABILITY & LIFE TESTING HANDBOOK

VOLUME 2

TABLE OF CONTENTS

CHAPTER 1- RELIABILITY AND CONFIDENCE LIMITS

FOR ONE-SHOT ITEMS OR

BINOMIAL (BERNOULLI) TRIALS ...... 1
1.1- THE BINOMIAL DISTRIBUTION ...... 1

1.2- THE CUMULATIVE BINOMIAL DISTRIBUTION ...... 9

1.3- BINOMIAL CONFIDENCE LIMITS ...... 22

1.4- EXACT BINOMIAL CONFIDENCE LIMITS ...... 47

CHAPTER 2- COMPARING TWO LOTS THROUGH BINOMIAL

TESTING ...... 59

2.1- WHEN AND HOW TO APPLY ...... 59

CHAPTER 3- SUSPENDED-ITEMS TEST, AND ANALYSIS

OF FIELD AND WARRANTY DATA ...... 77

3.1- OBJECTIVES AND APPLICABILITY ...... 77
3.2- METHODOLOGY AND APPLICATIONS ...... 78

3.3- TEST STOPPED WHEN ONLY PART OF THE SAMPLE

HAS FAILED - CENSORED TESTS ...... 105

CHAPTER 4- SUDDEN-DEATH TESTING ...... 147
4.1- OBJECTIVES AND APPLICABILITY ...... 147
4.2- METHODOLOGY AND APPLICATIONS ...... 148
4.3- STEP-BY-STEP PROCEDURE FOR SUDDEN-DEATH

TESTING AND DATA ANALYSIS ...... 150
4.4- RELATIONSHIP BETWEEN THE SUDDEN-DEATH LINE

AND THE POPULATION LINE ...... 153

4.5- CONFIDENCE BOUNDS ABOUT THE SUDDEN-DEATH

TEST POPULATION LINE ...... 154

4.6- SUDDEN-DEATH TEST DURATION ...... 161

CHAPTER 5- NONPARAMETRIC TESTING ...... 181
5.1- OBJECTIVES ...... 181
5.2-THE SUCCESS-RUN TEST ...... 181

5.3-THE CL-RANK TEST ...... 185

5.4-THE PERCENT-SURVIVING TEST ...... 187

5.5- THE SIGN TEST ...... 198

5.6- THE RUN AND RANDOMNESS TESTS ...... 202

5.7- COMPARISON OF TWO POPULATION MEANS USING

THEIR RANGES ...... 217

5.8- THE BINOMIAL-PEARSON RELIABILITY TEST ...... 220

5.9- BINOMIAL-PEARSON OVERLOAD-STRESS TEST ...... 223

5.10-THE WILCOXON-WHITE RANK-SUM TEST FOR TWO

INDEPENDENT SAMPLES...... 224

CHAPTER 6- ACCEPT-REJECT TESTING WITH FIXED TEST

TIME OR FIXED TEST FAILURES WHILE
MEETING BOTH THE CONSUMER'S AND THE
PRODUCER'S RISK REQUIREMENTS FOR THE

EXPONENTIAL CASE ...... 267
6.1- INTRODUCTION ...... 267
6.2- FIGURES 6.1 AND 6.2 APPROACH ...... 268
6.3- FIGURE 6.3 APPROACH ...... 271
6.4- JUSTIFICATION FOR USING FIGURE 6.3 TO OBTAIN

CONFIDENCE LIMITS ON THE MEAN LIFE ...... 274
6.5- USES OF FIGURES 6.1 AND 6.2 ...... 276
6.6- TO FIND mL1 . ...... 277

6.7- TO FIND THE ALLOWABLE NUMBER OF FAILURES, a,

GIVEN mL1 ...... 278

6.8- TO FIND mU1 ...... 279

6.9- TO FIND P (R) GIVEN mU1 ...... 280

6.10-USES OF FIGURE 6.3 ...... 280

6.11-THE OPTIMUM NUMBER OF TEST UNITS FOR

ACCEPT-REJECT TESTING WITH ZERO FAILURES

WHILE MEETING THE CONSUMER'S RISK

REQUIREMENT FOR THE EXPONENTIAL CASE ...... 286

6.12- THE OPTIMUM NUMBER OF TEST UNITS FOR
ACCEPT-REJECT TESTING WITH ONE OR MORE
FAILURES WHILE MEETING THE CONSUMER'S RISK

REQUIREMENT FOR THE EXPONENTIAL CASE ...... 289

CHAPTER 7- SEQUENTIAL PROBABILITY RATIO TESTS

(SPRT) FOR THE EXPONENTIAL CASE ...... 303
7.1- INTRODUCTION ...... 303
7.2- SPRT ...... 304
7.3- SPRT FOR THE EXPONENTIAL CASE ...... 306

7.4- THE DISTRIBUTION OF THE SUCCESSIVE SUMS OF

THE TIMES TO FAILURE FROM AN EXPONENTIAL

SEQUENTIAL TEST PROCESS ...... 315

7.5- CALCULATION OF THE CONFIDENCE LIMITS ...... 321

7.6- THE OPERATING CHARACTERISTIC CURVE FOR THE

SEQUENTIAL TEST PLAN ...... 337

7.7- EXPECTED TEST TIME IN THE SEQUENTIAL TEST ...... 344

7.8- MIL-HDBK-781 ...... 348

7.9- THE OPTIMUM TEST SAMPLE SIZE ...... 360

CHAPTER 8- SEQUENTIAL TESTING ON THE SCALE

PARAMETER OF THE WEIBULL DISTRIBUTION ...... 367

8.1- ACCEPT AND REJECT CRITERIA ...... 367

CHAPTER 9- ACCEPT-REJECT TESTS FOR THE

BINOMIAL CASE ...... 373
9.1- WHEN AND HOW TO APPLY ...... 373

9.2- CHARTED AND TABULATED TWO-RISK TEST PLANS

FOR ACCEPT-REJECT BINOMIAL TESTS ...... 378

CHAPTER 10- SEQUENTIAL TESTING FOR THE

BINOMIAL CASE ...... 389

10.1- INTRODUCTION ...... 389
10.2- TEST REQUIREMENTS ...... 390

10.3- BINOMIAL SEQUENTIAL TEST PLAN TABLES ...... 396

10.4- METHOD FOR TRUNCATING THE SEQUENTIAL

TESTING PLANS FOR THE BINOMIAL CASE ...... 397

CHAPTER 11- BAYESIAN MTBF AND RELIABILITY

DEMONSTRATION TESTS ...... 415
11.1- BAYESIAN CONCEPTS ...... 415

11.2- GENERAL PROCEDURE FOR FINDING

THE POSTERIOR DISTRIBUTION ...... 430

11.3- THE EXPONENTIAL PRIOR DISTRIBUTION

WITH EXPONENTIAL AND POISSON CONDITIONALS ...... 434
11.4- THE BETA AND GAMMA PRIOR DISTRIBUTIONS ...... 447

11.5- ASSESSMENT OF PRIOR DISTRIBUTIONS ...... 454

11.6- TWO-RISK REQUIREMENTS CRITERIA ...... 510
11.7- TEST PLANS, PROCEDURES AND COMPARISONS ...... 514

11.8- BAYESIAN RELIABILITY / MTBF DEMONSTRATION-

KEY CONCEPTS SUMMARY ...... 539
11.9- SINGLE PRIOR BELIEF BAYESIAN RELIABILITY

DEMONSTRATION ...... 540

11.10- NONIDENTIFIABLE POSTERIOR DISTRIBUTIONS ...... 557

CHAPTER 12- ACCELERATED RELIABILITY AND

LIFE TESTS ...... 605
12.1- WHAT IT IS, AND HOW IT IS APPLIED ...... 605

12.2- THE ARRHENIUS MODEL ...... 607

12.3- THE EYRING MODEL ...... 636

12.4- THE INVERSE POWER LAW MODEL ...... 647

12.5- THE COMBINATION MODEL ...... 650

12.6- THE GENERALIZED EYRING MODEL ...... 659

12.7- THE BAZOVSKY MODEL ...... 665

12.8- TEMPERATURE-HUMIDITY MODELS ...... 668

12.9- THE WEIBULL STRESS-LIFE MODEL ...... 670

CHAPTER 13- TEST SAMPLE SIZE DETERMINATION ...... 699
13.1- INTRODUCTION ...... 699
13.2- NORMAL DISTRIBUTION ...... 700

13.3- EXPONENTIAL DISTRIBUTION ...... 722

13.4- WEIBULL DISTRIBUTION ...... 738
13.5- BINOMIAL DISTRIBUTION ...... 759

APPENDICES ...... 779
APPENDIX A- RANK TABLES ...... 780
APPENDIX B- STANDARDIZED NORMAL DISTRIBUTION'S

AREA TABLES ...... 794
APPENDIX C- PERCENTAGE POINTS, F-DISTRIBUTION ...... 802
APPENDIX D- CRITICAL VALUES FOR VARIOUS

KOLMOGOROV-SMIRNOV (K-S) GOODNESS-

OF-FIT TESTS ...... 821
APPENDIX E- BINOMIAL OR ATTRIBUTE RELIABILITY TEST

CURVES FOR CONFIDENCE LEVELS, CL,

OF 50%, 80%, 90%, 95%, AND 99% ...... 831

INDEX ...... 837 ABOUT THE AUTHOR ...... ……… ...... 854