05 Statistics for Traffic Engineering (Traffic Engineering هندسة المرور & Prof. Saad...

CE 436 Traffic Engineering

Topic 4: Statistics for Traffic Engineers

(Chapter 7)

Prof. Saad AlGadhi

CE 436 –Traffic Engineering

King Saud University

email: salgadhi@ksu.edu.sa

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Figure 7.1 The Normal Distribution

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x N [ , 2 ]

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z N [ 0, 1]

Figure 7.2 Shifting the Normal Distribution to the Standard Normal Distribution (Spot Speed)

x N [ 55, 49 ]

= 55 mph

= 7 mph

Examples p. 127

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Table 7.3 The Standard Normal Distribution

Table 7.3 (continued) The Standard Normal Distribution

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Figure 7.1 The Normal Distribution

p ( ± 1.00) = 68.27 %

p ( ± 1.96) = 95.0 %

p ( ± 2.00) = 95.45 %

p ( ± 3.00) = 99.73 %

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Confidence Intervals (Bounds)

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Example

Consider the spot speed data of Table 10.3 (p. 210) The computed mean was 48.1 mph and the computed standard deviation was 4.95 mph.

Consider the following hypothesis:

Ho, the underlying distribution is normal with =48.1 mph and =4.95 mph. See Table 10.3 (page 210)

N=12 categories, f=N-1-g=12-1-2=9 (# of degrees of freedom), =0.05, 2=16.92 (from Table 7.11, p.145)

Computed 2=14.3574<16.92 == > cannot reject Ho

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Required Reading

Ch. 7: Statistical Applications in Traffic Engineering

All sections

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HW # 3

Problems #:

7-1

7-2

7-3 (a & b only)

Due: Next Wednesday

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