Statistics for Business and Economics (13th Edition)
13th Edition
ISBN: 9780134506593
Author: James T. McClave, P. George Benson, Terry Sincich
Publisher: PEARSON
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Textbook Question
Chapter 8.3, Problem 8.40ACI
Impact of red light cameras on car crashes. To combat red-light-running crashes many states have installed red light cameras at dangerous intersections to photograph the license plates of vehicles that run the red light. How effective are photo-red enforcement programs in reducing red-light-running crash incidents at intersections? The Virginia Department of Transportation (VDOT) conducted a comprehensive study of its photo-red enforcement program. In one portion of the study, the VDOT provided crash data both before and after installation of red light cameras at several intersections. The data (measured as the number of crashes caused by red light running per intersection per year) for 13 intersections in Fairfax County, Virginia, are given in the table. Analyze the data for the VDOT. What do you conclude?
| Intersection | Before Camera | After Camera |
| 1 | 3.60 | 1.36 |
| 2 | 0.27 | 0 |
| 3 | 0.29 | 0 |
| 4 | 4.55 | 1.79 |
| 5 | 2.60 | 2.04 |
| 6 | 2.29 | 3.14 |
| 7 | 2.40 | 2.72 |
| 8 | 0.73 | 0.24 |
| 9 | 3.15 | 1.57 |
| 10 | 3.21 | 0.43 |
| 11 | 0.88 | 0.28 |
| 12 | 1.35 | 1.09 |
| 13 | 7.35 | 4.92 |
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Background: To prevent crashes caused by running red lights, many states are installing cameras at
dangerous intersections. These cameras are used to take photographs of the license plates of vehicles that
run a red light. The Virginia Department of Transportation (VDOT) obtained data on the number of crashes
per year caused by running a red light at 13 intersections in Fairfax County, Virginia.
Source: Virginia Transportation Research Council, "Research Report: The Impact of Red Light Cameras
(Photo-Red Enforcement) on Crashes in Virginia", June 2007
Directions: Perform an appropriate significance test to determine whether or not the reduction in the
number of crashes was statistically significant.
1. Click on the Data button below to display the data. Copy the data into a statistical software package
and click the Data button a second time to hide it.
Data
Before After
3.7 1.26
0.1
0
4.55 1.69
2.4
1.94
2.09 3.24
2.5
2.72
0.83
0.24
3.05
1.67
3.21
0.33
1.08
0.18
1.25 0.99
7.25 5.02
191…
Background: To prevent crashes caused by running red lights, many states are installing cameras at
dangerous intersections. These cameras are used to take photographs of the license plates of vehicles that
run a red light. The Virginia Department of Transportation (VDOT) obtained data on the number of crashes
per year caused by running a red light at 13 intersections in Fairfax County, Virginia.
Source: Virginia Transportation Research Council, "Research Report: The Impact of Red Light Cameras
(Photo-Red Enforcement) on Crashes in Virginia", June 2007
Directions: Perform an appropriate significance test to determine whether or not the reduction in the
number of crashes was statistically significant.
RED
LIGHT
PHOTO
ENFORCED
1. Click on the Data button below to display the data. Copy the data into a statistical software package
and click the Data button a second time to hide it.
Data
Before After
3.5
1.46
0.47
0.1
0.39
0
4.55 1.69
2.6 2.04
2.39
3.14
2.5
2.62
0.83
0.14
3.25
1.57
3.41…
Background: To prevent crashes caused by running red lights, many states are installing cameras at
dangerous intersections. These cameras are used to take photographs of the license plates of vehicles that
run a red light. The Virginia Department of Transportation (VDOT) obtained data on the number of crashes
per year caused by running a red light at 13 intersections in Fairfax County, Virginia.
RED
LIGHT
PHOTO
ENFORCED
Source: Virginia Transportation Research Council, "Research Report: The Impact of Red Light Cameras
(Photo-Red Enforcement) on Crashes in Virginia", June 2007
Directions: Perform an appropriate significance test to determine whether or not the reduction in the
number of crashes was statistically significant.
1. Click on the Data button below to display the data. Copy the data into a statistical software package
and click the Data button a second time to hide it.
Data
Before
After
3.7
1.26
0.37
0.1
0.39
0
4.55
1.69
2.4
1.94
2.09
3.24
2.5
2.72
0.83
0.24
3.05
1.67
3.21…
Chapter 8 Solutions
Statistics for Business and Economics (13th Edition)
Ch. 8.2 - The purpose of this exercise is to compare the...Ch. 8.2 - Prob. 8.2LMCh. 8.2 - In order to compare the means of two populations,...Ch. 8.2 - Prob. 8.4LMCh. 8.2 - Prob. 8.5LMCh. 8.2 - Prob. 8.6LMCh. 8.2 - Independent random samples from normal populations...Ch. 8.2 - Two independent random samples nave been...Ch. 8.2 - Independent random samples of n1 = 233 and n2 =...Ch. 8.2 - Independent random samples from approximately...
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Gonzaga...Ch. 8.5 - Assuming that n1 = n2, find the sample sizes...Ch. 8.5 - Find the appropriate values of n1 and n2 (assume...Ch. 8.5 - Suppose you want to estimate the difference...Ch. 8.5 - Enough money has been budgeted to collect...Ch. 8.5 - Last name and acquisition timing. Refer to the...Ch. 8.5 - Homework assistance for accounting students. Refer...Ch. 8.5 - Vulnerability of relying party Web sites. Refer to...Ch. 8.5 - Conducting a political poll. A pollster wants to...Ch. 8.5 - Shared leadership in airplane crews. Refer to the...Ch. 8.5 - Solar energy generation along highways. Refer to...Ch. 8.5 - Angioplastys benefits challenged. Refer to the...Ch. 8.5 - Traffic sign maintenance. Refer to the Journal of...Ch. 8.6 - Use Tables V, VI, VII, and VIII in Appendix D to...Ch. 8.6 - Given v1 and v2, find the following probabilities:...Ch. 8.6 - For each of the following cases, identify the...Ch. 8.6 - For each of the following cases, identify the...Ch. 8.6 - Specify the appropriate rejection region for...Ch. 8.6 - Independent random samples were selected from each...Ch. 8.6 - Independent random samples were selected from each...Ch. 8.6 - Lobster trap placement. Refer to the Bulletin of...Ch. 8.6 - Prob. 8.81ACBCh. 8.6 - Mental health of workers and the unemployed. A...Ch. 8.6 - Drug content assessment Refer to Exercise 8.16 (p....Ch. 8.6 - Last name and acquisition timing. Refer to the...Ch. 8.6 - Prob. 8.85ACICh. 8.6 - Oil content of fried sweet potato chips. Refer to...Ch. 8.6 - Shopping vehicle and judgment. Refer to the...Ch. 8.6 - Is honey a cough remedy? 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