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).
- What is the z-score for the lower limit of 10.7 tonnes?
- What is the z-score for the upper limit of 26.0 tonnes?
- What does a negative z-score mean?
- z=(10.7−13)÷1.3=−1.77.
- z=(26.0−13)/1.3=10.
- A negative z-score means that the value is less than the mean.
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.