TY  - JOUR
PY  - 2012//
TI  - Planning sample sizes for before-after accident comparisons
JO  - Accident analysis and prevention
A1  - Sando, Thobias
A1  - Mohr, Donna
SP  - 826
EP  - 827
VL  - 45
IS  - 
N2  - Before-and-after safety studies are becoming more desirable in lieu of traditional cross-sectional studies in establishing crash modification factors, especially after the introduction of the first version of the Highway Safety Manual (2010). We present a simple method for estimating necessary sample sizes to obtain a target precision or power when the effect is represented as a proportional change in a Poisson rate. We also show that necessary sample sizes are not very different when full Bayesian models are implemented.<p />  <p>Language: en</p>
LA  - en
SN  - 0001-4575
UR  - http://dx.doi.org/10.1016/j.aap.2011.08.005
ID  - ref1
ER  -