1.
DR . SUDHIR CHANDRA SUR INSTITUE OF
TECHNOLOGY & SPORTS COMPLEX
Presentation on
Statistical Quality Control
Dept. of Automobile Engineering
(OE AUE 711A)
Submitted by-
Pu s p e n d r a Ku ma r
2 5 5 0 3 2 1 9 0 0 4
B.Te c h ( AU E) ( Fin a l Ye a r )
SUR TECH

2.
C O N T E N T S
 Introduction
 History
 Categories
 Variation in Quality
 Specification and
Control limits
 Process Capability
 Resources
i
i

3.
INTRODUCTION
St atist ical qualit y control is a n
applic ation o f statistic al tec hniques
to me as ure a n d inspec t the quality
o f a pr oduc t, s er vic e o r pr oc es s .

4.
HISTORY
St atist ical qualit y c ont rol was pioneer ed b y Walter A .
Shew hart a t Bell labor ator ies in the ear ly 1 9 2 0 s .
Shew har t d e ve lo p ed the con tro l c hart in
1924 and the c onc ept o f a s tatis tic al
c ontrol . H e c ons ulted w ith C olonel Les lie
E. Simon in the applic ation o f c ontr ol
c har ts to mu n itio ns manufac tur e a t the
Ar my’s Pic atinny Ar s enal in 1 9 3 4 .
W a l t e r A .
S h e w h a r t

5.
W. E dw a rd s D e m i n g i n v i t e d S h e w h a r t t o
s p e a k a t t h e G r a d u a t e S c h o o l o f t h e U . S .
D e p a r t m e n t o f A g r i c u l t u r e , a n d s e r v e d a s
t h e e d i t o r o f S h e wh a r t ' s b o o k “ S t a t i s t i c a l
M e t h o d f r o m t h e Vi e w p o i n t o f Q u a l i t y
C o n t r o l ( 1 9 3 9 ) ” w h i c h wa s t h e r e s u l t o f
t h a t l e c t u r e .
D eming w as an impor tant arc hitect o f
the quality c ontr ol s hor t c ours es that
trained American indus tries the new
tec hniques dur ing W W II.
W . E d w a r d s
D e m i n g

6.
CATEGORIES
Descriptive Statistics
D e s c r i p t i v e s t a t i s t i c s a r e u s e d t o
d e s c r i b e o r s u m m a r i z e t h e
c h a r a c t e r i s t i c s o f a s a m p l e o r d a t a
s e t , s u c h a s a v a r i a b l e ' s m e a n ,
s t a n d a r d d e v i a t i o n , o r f r e q u e n c y

7.
Statistical Process Control (SPC)
Acceptance Sampling
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 ( S P C ) i s d e f i n e d a s t h e u s e o f
s t a t i s t i c a l t e c h n i q u e s t o c o n t r o l a p r o c e s s o r p r o d u c t i o n m e t h o d .
A c c e p t a n c e s a m p l i n g i s a q u a l i t y c o n t r o l
p r o c e d u r e , wh i c h u s e s t h e i n s p e c t i o n o f
s m a l l s a m p l e s i n s t e a d o f 1 0 0 p e r c e n t
i n s p e c t i o n i n m a k i n g t h e d e c i s i o n t o
a c c e p t o r r e j e c t m u c h l a r g e r q u a n t i t i e s .

8.
VARIATION IN QUALITY
Va r i a t i o n i s a d i s p a r i t y b e t we e n a n a c t u a l m e a s u r e o f a p r o d u c t
c h a r a c t e r i s t i c a n d i t s t a r g e t v a l u e .
E x c e s s i v e v a r i a t i o n i s o u t s i d e t h e
u p p e r a n d l o we r a c c e p t a b l e l i m i t s
e s t a b l i s h e d f o r a p r o d u c t
s p e c i f i c a t i o n , wh i c h c a n l e a d t o
p r o d u c t d i s c a r d o r s a l v a g e .
T h e v a r i a t i o n m a y b e d u e t o
s u b s t a n d a r d q u a l i t y o f r a w
m a t e r i a l , c a r e l e s s n e s s i n t h e p a r t
o f o p e r a t o r, f a u l t i n m a c h i n e r y
s y s t e m , e t c .

9.
SPECIFICATION AND CONTROL LIMITS
S p e c i f i c a t i o n l i m i t s a r e t h e t a r g e t s s e t f o r t h e p r o c e s s / p r o d u c t
b y c u s t o m e r o r m a r k e t p e r f o r m a n c e o r i n t e r n a l t a r g e t . I n s h o r t
i t i s t h e i n t e n d e d r e s u l t o n t h e m e t r i c t h a t i s m e a s u r e d .
C o n t r o l l i m i t s o n t h e o t h e r
h a n d a r e t h e i n d i c a t o r s o f
t h e v a r i a t i o n i n t h e
p e r f o r m a n c e o f t h e p r o c e s s .
I t i s t h e a c t u a l v a l u e s t h a t
t h e p r o c e s s i s o p e r a t i n g o n .
I t i s t h e r e a l t i m e v a l u e .

10.
PROCESS CAPABILITY
E v a l u a t i n g t h e a b i l i t y o f a p r o d u c t i o n p r o c e s s t o m e e t o r e x c e e d
p r e s e t s p e c i f i c a t i o n s , i s k n o wn a s p r o c e s s c a p a b i l i t y. P r o c e s s -
c a p a b i l i t y c a n b e u s e d s t u d y t o a s s e s s t h e a b i l i t y o f a p r o c e s s t o
m e e t s p e c i f i c a t i o n s .
A s s e s s i n g P r o c e s s
C a p a b i l i t y :
S a m p l i n g S c h e m e E x a m p l e
A s s e s s i n g p r o c e s s c a p a b i l i t y i s n o t e a s y.
S o m e t e x t b o o k s t e a c h u s e r s t o w a i t u n t i l
t h e p r o c e s s r e a c h e s e q u i l i b r i u m , t a k e
r o u g h l y 3 0 s a m p l e s a n d c a l c u l a t e t h e i r
s t a n d a r d d e v i a t i o n ; h o we v e r, i t i s
d i ff i c u l t t o k n o w w h e n t h e p r o c e s s
r e a c h e s a s t a t e o f e q u i l i b r i u m a n d i f t h e
r e c o m m e n d e d s a m p l e s a r e
r e p r e s e n t a t i v e o f t h e p r o c e s s .

11.
RESOURCES
 h t t p s : / / www. i n t o u c h - q u a l i t y. c o m / b l o g / b r i e f - h i s t o r y - o f -
q u a l i t y - c o n t r o l
 h t t p s : / / s m a l l b u s i n e s s . c h r o n . c o m / r o b u s t n e s s - q u a l i t y -
c o n t r o l - m e t h o d - 6 2 0 7 6 . h t m l
 h t t p s : / / www. w h a t i s s i x s i g m a . n e t / c o n t r o l - l i m i t s - v s -
s p e c i f i c a t i o n - l i m i t s /
 h t t p s : / / a s q . o r g / q u a l i t y - r e s o u r c e s / p r o c e s s - c a p a b i l i t y

12.
THANK YOU