6.1 Quick revision

We strongly recommend trying these Quick revision questions before your tutorial.

A new method for evaluating bridge loads (O’Brien et al. 2018) used a simulation to compare the new method to an existing method. For the simulation, they modelled the gross vehicle mass (GVM) of trucks as having a normal distribution, with a mean of 13 tonnes and a standard deviation of 1.3 tonnes.

The Isuzu F-Series trucks are rated as having a GVM between 10.7 and 26.0 tonnes (depending on the configuration; in 2024).

  1. What is the z-score for the lower limit of 10.7 tonnes?
  2. What is the z-score for the upper limit of 26.0 tonnes?
  3. What does a negative z-score mean?
0 of 3 correct
  1. z=(10.713)÷1.3=1.77.
  2. z=(26.013)/1.3=10.
  3. A negative z-score means that the value is less than the mean.


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References

O’Brien EJ, Zhang L, Zhao H, Hajializadeh D. Probabilistic bridge weigh-in-motion. Canadian Journal of Civil Engineering. NRC Research Press; 2018;45(8):667–75.