Total quality management by Joseph Berk

Author:Joseph Berk [Berk, Joseph]
Language: eng
Format: epub
Tags: Total quality management.
Publisher: Sterling Pub.
Published: 1993-06-09T19:00:00+00:00

STATISTICS FOR NONSTATISTICIANS

115

Figure 7. Frequency Data for Height. This table shows the frequency of heights in each four inch range for the 30 people described in this chapter.

Number of People In Range

50-54 54-58 58-62 62-66 66-70 70-74 74-78 Height (inches)

Figure 8. Frequency Distribution for Height. This frequency distribution graphically portrays the data of Figure 7.

bell pattern. When Shewhart plotted 10,000 points, it's likely he saw a near-perfect bell shape.

The Mathematics of the Normal Curve

The normal curve can be described mathematically with the following equation:

y =

e - (x-u) 2 / 2 q 2

GV271

where:

y = the number of times a value occurs in the distribution

e = 2.7182, which is a constant that is the base of natural logarithms

x = the value whose frequency we are interested in rinding

u = the average value

a = the standard deviation

tc = 3.178, which is another constant

Figure 9 also shows the concept. At first glance, the above equation looks intimidating, but it really isn't. For our purposes, we can simply say that it represents a

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