> Declaring a hypothesis publicly and then gathering data to see if it’s supported or not is good science

Not for something like this. This study isn’t about running an experiment to see if treatment A or B is better. This is an observational study that is supposed to determine the prevalence of SARS-CoV-2 infection in the population. There is no hypothesis here - That is to say, there shouldn’t be anything to prove. Whatever answer you measure, you measure (ignoring any other data collection issues).

But if you declare “I think the rate of infection is X”, and you end up with a rate of X, then no one knows if you’ve really found the rate to be X or if you put your thumb on the scales.

This should have been a fact finding mission to establish some of the basic numbers that will be needed to design the next wave of experiments or to guide policy.