The 50% value for the WER as a threshold for the distinction between the 'pos' and 'neg' category is adopted from (Gabsdil, 2003), based on the fact that WER is affected by concept accuracy (Boros et al., 1996).
if a hypothesis is erroneous as far as its transcript is concerned   The baseline for our experiments is the behavior of the Town-Info spoken dialogue system that was used to collect the experimental data.