BERLIN (Reuters) - German Chancellor Angela Merkel made a better impression on voters in a television debate on Sunday than her center-left challenger Martin Schulz, a flash survey by broadcaster ZDF showed. The poll, conducted by Forschungsgruppe Wahlen during the first half of the debate and published shortly after it had finished, showed that Merkel was viewed as more credible by 33 percent compared to 17 percent for Schulz. According to a separate poll by Infratest Dimap for ARD television, Merkel came across as more competent, credible and likeable than Schulz. The only category where Schulz scored higher was for being more combative. 