Bayesian Networks for Probabilistic Inference and Decision Analysis in Forensic Science, 2nd Edition

9.3.2 Background data

Examinations in real-world circumstances are often affected by inefficiencies. Imagine a scenario where n distinct images captured from the recordings from a surveillance camera are available of a male individual and where it is of interest to estimate the height of that individual. A measured height of the individual obtained by the available camera is denoted Y and is assumed to have a Normal distribution. These measured heights are biased because of errors introduced by the context in which the images were taken, such as the posture of the individual, the presence or absence of headgear and the angles of the camera relative to the individual. Denote the bias by . There are two sources of variance and these are assumed independent. The first is the precision of the measurement devices (assumed constant across devices), denote their variance by . The second is the variation associated with the context and is denoted . Hence, .

The uncertainty about is modelled through ...