I see that we need to collect responses from a "representative" sample of building occupants making up at least 30% of the total occupants. I'm wondering if this means we have to do some sort of random sample to select 30% of the occupants and then make sure 100% of those selected answer OR if it's ok to just send the survey to 100% of the building occupants and allow for some self selection in the 30% of the whole building that respond. Thanks.