Cost-Effective Performance Measures for Travel Time Delay, Variation, and Reliability (2008) / Chapter Skim
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Pages 34-36
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From page 34... ...
is significantly different from the after mean. The test cannot be used for determining the significance of changes in the variance of travel time or delay, which is necessary to determine whether an improvement in the BI or other similar measure of reliability is statistically significant.
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From page 35... ...
The test begins with the specification of a null hypothesis that you hopefully will be able to reject: "The measured difference in mean travel time for the before and after conditions occurred by random chance. There really is no significant difference in the mean travel time between the before and after conditions." A statistic is computed for a selected level of confidence, and if the difference between the two means is less than that statistic, then the null hypothesis is accepted and it is concluded that there is insufficient evidence to prove that the after condition is better than the before condition.
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From page 36... ...
(Analysts should consult standard statistical textbooks for tables on the Type II errors associated with different confidence intervals and sample sizes.) 4.5 What to Do If the Null Hypothesis Cannot Be Rejected If the null hypothesis of no significant difference in the mean results for the before and after conditions cannot be rejected, the analyst has the following options: 1.
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