Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

652 Chapter 19 Probability and Statistics in Engineering

Density of

Air (kg /m

3

)

1.27

1.21

1.28

1.25

1.24

Coal from County Higher Heating

and State of Value (Btu /lbm)

Musselshell, Montana 12,075

Emroy, Utah 13,560

Pike, Kentucky 15,040

Cambria, Pennsylvania 15,595

Williamson, Illinois 13,710

McDowell, West Virginia 15,600

Heating Value

Source of Gas (Btu /lbm)

Pennsylvania 23,170

Southern California 22,904

Ohio 22,077

Louisiana 21,824

Oklahoma 20,160

Number of Hours the

Light Bulb Functioned

before Failing Frequency

700 15

800 20

900 34

1000 28

1100 22

1200 16

Viscosity of

Engine Oil

(Ns/m

2

)

0.15

0.10

0.12

0.11

0.14

19.16. Imagine that you and four of your classmates have mea-

sured the density of air and recorded the values shown

in the accompanying table. Determine the average,

variance, and standard deviation for the measured den-

sity of air.

19.21. Typical heating values of natural gas from various parts

of the U.S. are shown in the accompanying table. Cal-

culate the average, variance, and standard deviation for

the given data.

19.17. Imagine that you and four of your classmates have mea-

sured the viscosity of engine oil and recorded the val-

ues shown in the accompanying figure. Determine the

average, variance, and standard deviation for the mea-

sured viscosity of oil.

19.18. Assuming a standard normal distribution

(Table19.11), what percentage of the data falls between

1.5 s to 1.5 s?

19.19. Assuming a standard normal distribution

(Table19.11), what percentage of the data falls between

0.5 s to 0.5 s?

19.20.Typical heating values of coal from various parts of the

U.S. are shown in the accompanying table. Calculate

the average, variance, and standard deviation for the

given data.

19.22.As an electrical engineer, you have designed a new effi-

cient light bulb. In order to predict its life expectancy,

you conducted a series of experiments on 135 of these

light bulbs and gathered the following data. Plot the

data and calculate the mean and standard deviation.

Source:Babcock and Wilcox Company, Stream: Its Generation

and Use.

Source:Babcock and Wilcox Company, Stream: Its Generation

and Use.

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