Statistical process control technique with example - xbar chart and R chart
14
STATISTICAL PROCESS CONTROL
-
Upload
kevin-richard -
Category
Education
-
view
303 -
download
1
description
SPC technique with an example make it simple
Transcript of Statistical process control technique with example - xbar chart and R chart
STATISTICAL PROCESS CONTROL
STATISTICAL PROCESS CONTROL (SPC)
• Statistical process control (SPC) is a method of quality control
which uses statistical tools
• SPC is applied in order to monitor and control a process
• SPC can be applied to any process where the "conforming
product" (product meeting specifications) output can be
measured
• It is used to ensure the continuous improvement in quality of
the products, services and productivity in the workforce
CONTROL CHARTS :
• Control charts are also known as Shewhart charts (after Walter A.
Shewhart) or process-behavior charts
• Control charts are the tools in SPC, used to determine if a
manufacturing or business process is in a state of statistical control.
Question :
A manufacturer produces digital watches. Every 2 hours ,a sample of six
watches is selected randomly to be tested. Each watch is run for exactly
15 minutes and is timed by an accurate , precise timing device. Because
of the variation among watches, they do not all run the same. Shown
here are the data from eight different samples given in minutes. Use
these data to construct chart and R chart. Observe the results and
comment on whether the process is in control
Sample 1 Sample 2 Sample 3 Sample 4
15.01 15.03 14.96 15
14.99 14.96 14.97 15.01
14.99 15.01 14.96 14.97
15.00 15.02 14.99 15.01
14.98 14.97 15.01 14.99
14.99 15.01 14.98 14.96
Sample 5 Sample 6 Sample 7 Sample 8
15.02 15.02 15.03 14.96
15.03 15.01 15.04 14.99
14.99 14.97 15.03 15.02
15.01 15.00 15.00 15.01
15.02 15.01 15.01 14.98
15.01 14.99 14.99 15.02
Formulas used:
Calculation :Sample 1 Sample 2 Sample 3 Sample 4
15.01 15.03 14.96 15
14.99 14.96 14.97 15.01
14.99 15.01 14.96 14.97
15.00 15.02 14.99 15.01
14.98 14.97 15.01 14.99
14.99 15.01 14.98 14.96
Mean 14.99 15.00 14.98 14.99
Range 0.03 0.07 0.05 0.05
Contd..Sample 5 Sample 6 Sample 7 Sample 8
15.02 15.02 15.03 14.96
15.03 15.01 15.04 14.99
14.99 14.97 15.03 15.02
15.01 15.00 15.00 15.01
15.02 15.01 15.01 14.98
15.01 14.99 14.99 15.02
Mean 15.01 15.00 15.02 15.00
Range 0.04 0.05 0.05 0.06
Control Charts : Interpretation
1 2 3 4 5 6 7 814.96
14.97
14.98
14.99
15
15.01
15.02
15.03
X bar chart
sample
Sam
ple
Mea
n
1 2 3 4 5 6 7 80
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
R chart
Sample
Rang
e
THANK YOU
