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E F F E C T O F T H E L E V E L O F S T A T I S T I C A L P R O C E S S 
C O N T R O L (SPC) P R A C T I S E S ON Q U A L I T Y 
P E R F O R M A N C E 
U W V E R S I T Y O F M O R J T U W A . SRI L A N K A 
M O R A T U W A 
W.M.S.K. Wijebahu 
Reg No.8/8717 
Dissertation submitted in partial fulfillment of the requirements for the degree Master 
of Science 
University of Moratuwa 
IIU 
104517 
Department of Textile and Clothing Technology 
University of Moratuwa 
Sri Lanka 
June 2012 
G i l 
104517 
D E C L A R A T I O N 
" I declare this is my own work and this thesis does not incorporate without 
acknowledgement any material previously submitted for a Degree or Diploma 
in any other University or institute of higher learning and to the best of my 
knowledge and belief it does not contain any material previously published or 
written by another person except where the acknowledgement is made in the 
text. 
Also, I hereby grant to University of Moratuwa the non-exclusive right to 
reproduce and distribute my thesis/dissertation, in whole or in part in print, 
electronic or other medium. I retain the right to use this content in whole or 
part in future works (such as articles or books). 
The supervisor should certify the thesis with the following declaration. 
The above candidate has carried out research for the Masters thesis 
under my supervision. -
; Date: Signature: 
Signature of the supervisor: Date 
ABSTRACT 
Statistical process control (SPC) is a powerful technique for improving process 
quality by systematically eliminating special or assignable causes of variation. SPC is 
not a simple and automatic task. The successful application of SPC requires focused 
to following ingredients. Such as management commitment, usage of control charts 
,identification of critical measurement , operator responsibility ,process definition 
,training for SPC ,teamwork ,organizational cultural change ,update the knowledge of 
process ,audit the SPC practices and performance ,computers and SPC software 
packages. 
The purpose of this study is to investigate the level of SPC practices and the impact 
on organizational performance in terms of quality. The study mainly focus to lean 
applied apparel manufactures in Sri Lanka to analysis out the level of SPC practicing 
as well as the effect of SPC to the performance of key quality factors. The study was 
conducted utilizing the statistical process control integrated with quality performance 
questionnaire which was previously tested by researchers. ' 
This study describes the process and outcomes of the 11 ingredients underlying the 
SPC practices. Data collected form 20 lean implemented apparel industry in Sri Lanka 
and data analyzed to find the level of statistical process control practicing and the 
quality performance. Used SPSS software calculated standard deviation, correlations 
and the mean value. Further used to Excel sheet to analyze collected the data. 
The collected data was analyzed according to company vise to measure the SPC 
practicing level. The key quality performances were analysis with level of the SPC 
practicing. The result was discussed according to the collected data and also 
discussed. - • -
According to the result the lean applied apparel manufacturer are practicing SPC 
78.40 % and there is positive trend in key quality performance with SPC practicing 
level. 
A C K N O W L E D G E M E N T 
I wish to all those who have contributed to the accomplishments of this task: Ganga, 
my loving wife, who has been by my side and has been a constant motivation for me 
to work until completion of this project. Her part in my completion of this dissertation 
has been monumental. ^ 
I am greatly indebted to my loving parents R.P.A Rajapaksha , A Panagoda (Mother-
in-law) , and Upali Panagoda (Father-in-law), for their support, prayers, and belief in 
me, that I achieve in my dissertation. My wife G E Panagoda ,my son Sandaru 
Wijebahu and my daughter Kalani Wijebahu, have been there in spirit, and in prayers 
for me to complete this goal. 
Dr .Dhramasri Wickramasinghe, my supervisor, who has been a strong force of 
inspiration for me, completing this project. I specially offer thank to my supervisor for 
the support and the encouragement. And, to my friend Afham , who helped in my 
survey and offered support to collect data and analysis the data, you've been a true 
friend. 
I do wish to convey my sincere gratitude to Sri Lanka Institute of Textile and Apparel 
for sponsoring me for Master degree programme and owe thank to Nishantha Team 
Leader , Director (Training and Technical) Mr D P L P Jayaweera and Director 
(Administration) Mr Vasantha Wijerathne to encouragement. Finally I convey my 
thanks to employees' response my questiormaire. 
iii 
C O N T E N T 
Declaration of the candidate & supervisor i 
Abstract i i 
Acknowledgments i i i 
Content iv 
List of Figure ! vi 
List of Table , vi i 
CHAPTER 1: Introduction 1 
1.0 Introduction to the Problem 1 
1.1 Background of the Study 4 
1 
1.2 Statement of the Problem 4 
1.3 Purpose of the Study 4 
1.4 Objective of the Study 5 
1.5 Significance of the Study 5 
CHAPTER 2: Literature Review 6 
2.0 Introduction 6 
2.1 Statistical process control 6 
2.2 Organizational performance 13 
2.3 Quality performance 13 
2.4 Lean manufacturing 15 
2.5 Lean manufacturing and SPC 17 
2.6 Statistical process control and quality performance 18 
2.7 Chapter summery 19 
CHAPTER 3: Methodology 21 
3.0 Introduction 21 
3.1 Theoretical Framework ^ 21 
3.2 Theoretical Framework for objectives 22 
3.3 Sampling Design 22 
3.4 Parti6ipant Group 23 
iv 
3.5 Questionnaires Development 24 
3.6 Data Collection 24 
3.7 Data Analysis 25 
3.8 Limitations of Methodology 26 
CHAPTER 4: RESULT AND DISCUSTION i 27 
4.0 Introduction 27 
4.1 Level of implementation and practices Statistical process control 27 
4.1.1 Level of management commitment 27 
4.1.2 Level of identification of critical measurement 2 8 
4.1.3 Level of operator responsibility 2 9 
4.1.4 Level of process definition ' 3 0 
^ 4.1.5 Level of control chart usage ; 3 0 
. 4.1.6 Level of training 3 1 
4.1.7 Level of team work 32 
4.1.8 Level of organization culture change 33 
4.1.9 Level of update knowledge of process 33 
4.1.10 Level of auditor review of SPC 3 4 
4.1.11 Level of computer software usage 35 
4.2 Level of SPC practices 3 6 
4.3 Level of Quality performance 3 7 
4.3.1 Level of SPC practices and the mean monthly rejection 37 
4.3.2 Level of SPC practices and the mean rework percentage 39 
4.3.3 Level of SPC practices and the average audit pass rate 40 
4.3.4 Level of SPC practices and the average final audit pass rate 42 
CHAPTER 5: Conclusion, Discussion and recommendations 4 4 
5.0 Introduction 4 4 
5.1 Summery of the Discussion ^ 4 4 
5.3 Conclusion 4 5 
REFERENCES . 4 6 
4 
List of Figures 
Figure 2.1: Basic function of SPC 0 8 
Figure 3.1: Theoretical Farm work 2 2 
Figure 4.1: Mean value variation of the management commitment 2 8 
Figure 4.2: Mean value variation of identification of critical measurement 28 
Figure 4.3: Mean value variation of the operator responsibility 2 9 
Figure 4.4: Mean value variation of process identification 3 0 
Figure 4.5: Mean value variation of the control chart usage 3 1 
Figure 4.6: Mean value variation of the training SPC 3 1 
Figure 4.7: Mean value variation of team work 3 2 
Figure 4.8: Mean value variation of the organization culture change 3 3 
Figure 4.9: Mean value variation of the update knowledge of process 3 4 
Figure 4.10: Mean value variation of the audit or review of the SPC 34 
Figure 4.11: Mean value variation of the computer software usage 3 5 
Figure 4.12: Level of the SPC practices 37 
Figure 4.13: Average SPC Level Vs mean rejection percentage 38 
Figure 4.14: Average SPC Level Vs mean average rework percentage 39 
Figure 4.15: Average SPC Level Vs mean average daily audit pass percentage 41 
Figure 4.16: Average SPC Level Vs mean average final audit pass percentage 42 
VII 
APPENDIX I 48 
APPENDIX I I 53 
1 
» 
vi 
List of Tables 
Table 3.1: Question numbers and Ingredient of SPC 23 
Table 4.1: Mean value and Standard deviation of level of the SPC 3 6 
Table 4.2: The correlation between the level of SPC implementation and 38 
practices with the average monthly rejection percentage 
Table 4.3: The correlation between the level of SPC practices with the average 40 
rework percentage « 
Table 4.4: The correlation between the level of SPC practices with the average 41 
audit pass rate per day 
Table 4.5: The correlation between the level of SPC practices with the average 42 
final audit pass percentage 
viii