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The following data show spot speeds collected at a section of highway located in a residential area before and after an increase in speed enforcement activities. (All speeds are in mi/h.) Before After Before After 44 27 34 21 38 36 35 21 36 23 32 37 41 40 26 26 36 40 38 33 28 32 41 23 32 27 31 24 38 31 36 23 33 22 36 26 44 35 29 23 36 27 31 20 33 18 38 22 40 25 31 26 39 31 33 32 38 33 41 35 Using the student's t-test, determine whether there was a statistically significant difference in the average speeds at a significance level of a = 0.05 (the 95-percent confidence level.) O Yes, there was a statistically significant difference in the average speeds. ○ No, there was not a statistically significant difference in the average speeds. Also report, for both the before and after cases, the mean speed, standard deviation, 85th-percentile speed, and percentage of traffic exceeding the posted speed limit of 30 mi/h. (Enter all speeds and standard deviations in mi/h. Round your 85th-percentile speeds to at least the nearest integer.) Before: mean speed standard deviation 85th-percentile speed mi/h mi/h mi/h percentage exceeding limit % After: mean speed standard deviation mi/h mi/h 85th-percentile speed mi/h percentage exceeding limit %

The following data show spot speeds collected at a section of highway located in a residential area before and after an increase in speed enforcement activities. (All speeds are in mi/h.) Before After Before After 44 27 34 21 38 36 35 21 36 23 32 37 41 40 26 26 36 40 38 33 28 32 41 23 32 27 31 24 38 31 36 23 33 22 36 26 44 35 29 23 36 27 31 20 33 18 38 22 40 25 31 26 39 31 33 32 38 33 41 35 Using the student's t-test, determine whether there was a statistically significant difference in the average speeds at a significance level of a = 0.05 (the 95-percent confidence level.) O Yes, there was a statistically significant difference in the average speeds. ○ No, there was not a statistically significant difference in the average speeds. Also report, for both the before and after cases, the mean speed, standard deviation, 85th-percentile speed, and percentage of traffic exceeding the posted speed limit of 30 mi/h. (Enter all speeds and standard deviations in mi/h. Round your 85th-percentile speeds to at least the nearest integer.) Before: mean speed standard deviation 85th-percentile speed mi/h mi/h mi/h percentage exceeding limit % After: mean speed standard deviation mi/h mi/h 85th-percentile speed mi/h percentage exceeding limit %

Traffic and Highway Engineering
Traffic and Highway Engineering
5th Edition
ISBN:9781305156241
Author:Garber, Nicholas J.
Publisher:Garber, Nicholas J.
Chapter4: Traffic Engineering Studies
Section: Chapter Questions
Problem 8P
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The following data show spot speeds collected at a section of highway located in a residential area before and after an increase in speed enforcement activities. (All speeds are in mi/h.) Before After Before After 44 27 34 21 38 36 35 21 36 23 32 37 41 40 26 26 36 40 38 33 28 32 41 23 32 27 31 24 38 31 36 23 33 22 36 26 44 35 29 23 36 27 31 20 33 18 38 22 40 25 31 26 39 31 33 32 38 33 41 35 Using the student's t-test, determine whether there was a statistically significant difference in the average speeds at a significance level of a = 0.05 (the 95-percent confidence level.) O Yes, there was a statistically significant difference in the average speeds. ○ No, there was not a statistically significant difference in the average speeds. Also report, for both the before and after cases, the mean speed, standard deviation, 85th-percentile speed, and percentage of traffic exceeding the posted speed limit of 30 mi/h. (Enter all speeds and standard deviations in mi/h. Round your 85th-percentile speeds to at least the nearest integer.) Before: mean speed standard deviation 85th-percentile speed mi/h mi/h mi/h percentage exceeding limit % After: mean speed standard deviation mi/h mi/h 85th-percentile speed mi/h percentage exceeding limit %
Transcribed Image Text:The following data show spot speeds collected at a section of highway located in a residential area before and after an increase in speed enforcement activities. (All speeds are in mi/h.) Before After Before After 44 27 34 21 38 36 35 21 36 23 32 37 41 40 26 26 36 40 38 33 28 32 41 23 32 27 31 24 38 31 36 23 33 22 36 26 44 35 29 23 36 27 31 20 33 18 38 22 40 25 31 26 39 31 33 32 38 33 41 35 Using the student's t-test, determine whether there was a statistically significant difference in the average speeds at a significance level of a = 0.05 (the 95-percent confidence level.) O Yes, there was a statistically significant difference in the average speeds. ○ No, there was not a statistically significant difference in the average speeds. Also report, for both the before and after cases, the mean speed, standard deviation, 85th-percentile speed, and percentage of traffic exceeding the posted speed limit of 30 mi/h. (Enter all speeds and standard deviations in mi/h. Round your 85th-percentile speeds to at least the nearest integer.) Before: mean speed standard deviation 85th-percentile speed mi/h mi/h mi/h percentage exceeding limit % After: mean speed standard deviation mi/h mi/h 85th-percentile speed mi/h percentage exceeding limit %
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