Transportation Statistics and Microsimulation

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7Chapter

Inferences

Hypothesis Testing and

Interval Estimation

7.1 INTRODUCTION

Oen transportation professionals are asked to make specic statements

regarding the transportation system. For example:

Are average speeds on a freeway within federal guidelines?

Has a safety improvement actually led to a reduction in crashes?

Are the contractors meeting the specications in the contract?

Are ambulances reaching their destinations within their target time?

Is congestion on one roadway worse than another?

Over the years much eort has been exerted to build statistical models

that help answer these types of questions. Curve tting and density estima-