The researchers kept their identities secret because, if they had revealed that their purpouse was to conduct an experiment on the behaviours of the people in the bar, it might have triggered that some people changed their usual attitudes because they know that their 'figures' will be kept in a record.
Maybe some people will drink less as they feel embarrased if some other person is testing how many beers they end. Others, might want to prove themselves 'strong' and drink much more than usual. People change their behaviour sometimes when they are aware that they are watched. This is called the observer effect.
The religion which is gaining more members in Europe than any other is Islam: it is a combination of Immigration, high birth rate among the Muslim population and new converts. In comoparison, Christianity is loosing members because the Christian population is becoming more and more secular.
By protecting his identity to the public and not always coming to the report place
