Injury and ill health rates over time are examined using smoothing techniques which aim to reduce irregularities (random fluctuations) in the time series. A Generalised Additive Model (GAM), which is an extension of a Generalised Linear Model (GLM) with 'smooth' terms, has been used where the smoothed term is the year. The modelling was completed using the mixed generalised additive vehicle package for GAMs, supplied with the software R1.
A downward or upward trend is recorded when two conditions are met:
Where no downward or/upward trend is indicated one of these conditions has not been met.
1. Wood, S N (2006): Generalised Additive Models: An introduction to R.