Total Quality Management - CII Institute of Logistics

Total Quality Management
3. Things vary according to a definite pattern
If you want to see this pattern take shape, all you need to do is record the measurements
of a dimension on parts from one of your operations on your job. If you record them in
tally form, you will see a pattern begin to form after you have measured and recorded
several parts. An easy way to demonstrate this principle is to roll a pair of dice
fifty or more times and record the total number of spots that come up in each throw.
After a while you will see a pattern begin to form. This pattern sometimes called a
frequency distribution, and is shown in Figure 4.1
12 x
11 x
10 xxxxx
9 xxxx
8 xxxxx xxx
7 xxxxx xxxxx x
6 xxxxx Xx
5 xxxxx x
4 xxxx
3 xx
2 x
Figure 4.1 Frequency Distribution
A frequency distribution curve is formed by enclosing the tally marks in a curved line.
This curve shows that there are more measurements or numbers in the middle and
fewer as you go away from the middle. As you can see, the curve is shaped like a bell
(see Figure 4.2)
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