vdoc

Chapter 18: A. Basic Statistics and Applications 211
Continued
15.5 m = 15.8 16.1
0.3 = 2s 0.3 = 2s
m – 2s
m – 2s
Figure 18.4 Amount of soft drink contained in a bottle.
EXAMPLE 18.12
At the end of every fiscal year, a manufacturer writes off or adjusts its financial records
to reflect the number of units of bad production occurring over all lots of production
during the year. Suppose that the dollar values associated with the various units of bad
production form a bell-shaped distribution with mean x – = $35,700 and standard deviation
s = $2,500. Find the percentage of units of bad production that has a dollar value
between $28,200 and $43,200.
Solution:
From the information provided to us we have x – = $35,700 and s = $2,500
Since the limits $28,200 and $43,200 are three standard deviations away from the
mean, comparing Figure 18.5 with Figure 18.3, we see that approximately 99.7 percent of
the units of bad production had a dollar value between $28,200 and $43,200.
Part IV.A.2
28,200
X – = 35,700
43,200
X – 7500 = 3s 7500 = 3s
– 3s
X – + 3s
Figure 18.5 Dollar value of units of bad production.