1. Global Business Management Group
Statistical Process Control
INTRODUCTION

2. Why we use control charts ?
Global Business Management Group
Statistical Process Control
What is SPC ?
What is VSC ?
Why we use control charts ?
Plotting of control chart ...

3. Statistical Process Control
Global Business Management Group
Global Business Management Group
Statistical Process Control
The Arithmetic mean :
Most of the time when we refer to the average of something we are talking about arithmetic mean only. To find out the arithmetic mean , we sum the values and divide by the number of observation.
Advantages : it's a good measure of central tendency.It easily understood by most people
Disadvantages :- Although the mean is reliable in that it reflects all the values in the data set, it may also be affected by extreme values that are not representative of the rest of the data.

4. Global Business Management Group
Statistical Process Control
The Median :
The median is a single value from the data set that measures the central item in the set of numbers.Half of the item lie above this point and the other half lie below it.
We can find median even when our data are qualitative descriptions.
For example we have five runs of the printing press the results of which must be rated according to the sharpness of the image.
Extremely sharp, very sharp, sharp slightly blurred, and very blurred.

5. Global Business Management Group
Statistical Process Control
Mode :-
The mode is a value that is repeated most often in the data set. Infect it is the value with highest frequency.

6. Statistical Process Control
Global Business Management Group
Statistical Process Control
Average Income
Country X
Country Y
10,000 Rs/Month
11000 Rs/Month
Which country is ECONOMICALLY more stable ???

7. Global Business Management Group
Statistical Process Control
Country X Country Y
Avg
Std dev

8. Measure of SPREAD sigma Statistical Process Control
Global Business Management Group
Statistical Process Control
Standard Deviation is the
sigma
Measure of SPREAD

9. Global Business Management Group
Statistical Process Control
 (sigma) = √
(x-x ) + (x-x ) + … (x-x )
(n - 1) _ 1 2 n 2 2 2

10. Statistical Process Control
Global Business Management Group
Statistical Process Control
Plot HISTOGRAM for following DATA

11. Normal Distribution Curve
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Statistical Process Control
Normal Distribution Curve

12. Global Business Management Group
Statistical Process Control
Properties of a normal model curve :-
It is symmetrical , unimodel and bell shaped.
The values of mean , median and mode are identical.
It is uniquely determined by the two parameters , namely mean and standard deviation.
In the family of normal curves smaller the standard deviation , higher will be the peak.
If the original observations follow a normal model with mean mu and std dev sigma then the averages of random sample of size n drawn from this distribution will also follow a normal distribution. The mean of the new model is same as the original model I.e mu but the standard deviation gets reduced to  (sigma)/root "n"

13. Global Business Management Group
Statistical Process Control
99.73%
+/-3 sigma
95.45%
+/- 2 sigma
68.26%
+/- 1 sigma
2.14%
13.6%
34.13%
34.13%
13.6%
2.14%

14. Global Business Management Group
Statistical Process Control
Description of a
NORMAL DISTRIBUTION
LOCATION:
The central tendency
it is usually expressed as the
AVERAGE
SPREAD:
The dispersion
it is usually expressed as SIGMA

15. Global Business Management Group
Statistical Process Control
A Process Control System
THE PROCESS
INFORMATION ABOUT PROCESS
ACTION ON THE PROCESS
Local Action - Special cause
Action on the System - Common cause
ACTION ON THE OUTPUT

16. DEMING’s Funnel Experiment
Global Business Management Group
Statistical Process Control
DEMING’s Funnel Experiment

17. Variation :- Common cause and Special Cause
Global Business Management Group
Statistical Process Control
Variation :- Common cause and Special Cause
In order to effectively use of process control measurement data, it is important to understand the concept of variation.
No two characteristic or products are exactly alike, because any process contain many source of variability.
Some source of variation in the process cause short-term, piece to piece difference's - e.g., backlash and clearance with in a machine and its fixturing. Other sources of variation end to cause changes in the output only over along period of time, either gradually as with tool or machine wear, step with procedural changes, or irregularly, as with environmental changes such as power surge. Therefore the time period and condition over a which measure are made will effect the amount of the total variation that will be present.
Common cause refer to the many sources of variation within a process that has a stable and repeatable distribution over a time. This is called “STATE of STATISTICAL CONTROL” .
Common cause behave like a stable system of chance cause. If only common cause of variation are present and do not change, the output of a process is predictable.
The change in the process due to the SPECIAL cause can either be detrimental or beneficial. When detrimental, they need to be identified and removed. When beneficial, they should be identified and made a permanent part of the process.

18. Global Business Management Group
Statistical Process Control
SPECIAL CAUSE
LOCAL ACTION
COMON CAUSE
ACTION on SYSTEM

19. Global Business Management Group
Statistical Process Control
CONTROL CHART
When you need to discover how much variability in a process is due to unique events/individual actions in order to determine whether a PROCESS IS IN STATISTICAL CONTROL
Variable Data
Attribute Data
p Chart
np Chart
c Chart
u chart
X bar - R chart
X-s Chart
X- Mr Chart

20. X R Statistical Process Control = X+X+X+…X n R+R+R+…R = n
Global Business Management Group
Statistical Process Control X =
X+X+X+…X n n
R+R+R+…R R = n n
Upper Control Limit
UCL = X + A R 2
Lower Control Limit
LCL = X - A R 2
Center Line for Average Chart is X double bar
and
Center line for Range chart is R bar

21. Statistical Process Control
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Statistical Process Control
The p Chart = Proportion Defective
p =
Number of rejects in a subgroup
Number inspected in subgroup
p =
Total Number of rejects
Total Number inspected _

22. INTERPRETING CONTROL CHARTS
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Statistical Process Control
INTERPRETING CONTROL CHARTS

23. Global Business Management Group
Statistical Process Control
COMMON QUESTION TO ASK
WHEN INVESTIGATING AN
OUT OF CONTROL PROCESS

24. Process Capability  Cpk = Cp = Statistical Process Control
Global Business Management Group
Statistical Process Control
Process Capability
Tolerance band
6 * 
Cp =
(USL-X d bar), (X d bar - LSL)
Cpk =
Min of
3* 
3* 