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Title of Thesis

Tasneem Ali
Institute/University/Department Details
University f Karachi/ Department of Statistics
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
statistical control, statistical process control (spc), average run lengths (arls), quality system, quality control, quality cost

Statistical Process Control (SPC) is an effective tool of monitoring the process and detecting the causes, which shifts the process from the target. One of the SPC’s important tools is control chart. The process failure mechanism follows a weibull Distribution. The economic aspect introduced in the control chart makes it more efficient to monitor the performance of the system. Most quality control experimenters wish to study the quality characteristic having some symmetrical distributions due to readily available control charts. In reality, practitioners must focus on the true underlying distribution of the quality characteristic, which in most cases are asymmetristic, which in most cases are asymmetrical. The study is envisaged to monitor the process economically during on-line and while it is off-line

The economic aspect of control chart depends on three design parameters; sample size, sampling interval and width of the control chart. We have applied pattern search technique to estimate the optimal economic design parameters. This technique helps us to choose the best economic design parameters, for which the cost function is minimum. It is also shown that choosing any possible combination of parameters for two-parameter weibull distribution but keeping the mean rate fixed, does not affect the optimization of the economic design parameters. The study is further extended to find the optimal economic design parameters in various situations of production being continued or ceased during the search of the assignable cause and the repair of the process

The sensitivity analysis of the design parameters is carried out by changing the magnitude of shift, cost and time input variables. It is also based on types of errors, OC curves and the Average Run Lengths (ARLs)

The second part of the study focuses on the offline quality control. In this part, we have enumerated the loss incurred to the producer as well as to the customer when the products are shipped to the customer with or without inspection. In this case the quality characteristic is a truncated weibull variable and the cost function depends only on one decision variable. The sensitivity analysis is carried out for the loss function on the shift. The comparative study is also based on Type I, Type-II errors, OC curves and ARLs

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1919.39 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents 0
150.09 KB
2 1 Introduction Of Quality Control 1
205.43 KB
  1.1 Introduction 1
  1.2 Historical Review 2
  1.3 Quality And Quality System 3
  1.4 Scope Of Total Quality Control 5
  1.5 Quality System 7
  1.6 Quality Cost 7
  1.7 Statistical Quality Control 10
  1.8 Statistical Process Control 13
  1.9 Control Chart 15
  1.10 Aim Of The Study 19
3 2 Economic Design Of Control Charts 24
220.92 KB
  2.1 Introduction 24
  2.2 Process Characteristics 25
  2.3 Cost Parameters 26
  2.4 Early Work On Semi Economic Design 29
  2.5 Introduction Of Economic Models Of X Control Charts 36
  2.6 Single Assingnable -Cause Models 36
  2.7 Other Process Models 42
  2.8 A Unified Approach Of The Economic Design Of Control Charts 49
4 3 Modification And Estimation Of Economic Design Parameters 50
575.29 KB
  3.1 The Lorenzen -Vance Model 50
  3.2 Different Types Of Control Charts 57
  3.3 Model Assumptions 59
  3.4 Minimizing The Cost Function 61
  3.5 Extension Of Lorenzen And Vance Model 65
  3.6 Optima Economic Design For Weibull Characteristics 92
5 4 Economic Design Of Truncated Distribution Based On Quality Loss Function 100
505.12 KB
  4.1 Quality Loss Function 100
  4.2 Quadratic Loss Function 112
  4.3 Loss Function And Specification Limits 116
  4.4 Role Of Truncation In Economic Design Of Control Charts 118
  4.5 Optimization Model Fro General Situation 122
  4.6 Truncated Weibull Distribution 125
  4.7 S-Type Weibull Quality 146
6 5 Suggestions 163
61.15 KB
7 6 References 170
489.08 KB