I need to make a random selection of mosques in a large city for a public health survey. I have a map that identifies a thousand of them, but many are unmapped, so I don't know what my 'universe' is, so I can't get a random sample. I'm considering dividing up the city into sections of equal area, taking a sample of those areas, and walking them to map missing mosques. Then I'll do a random selection of mosques from among the ones in my sample areas. Question 1) Have I gone off the rails so far?
To save on shoe leather, I would prefer to select fewer, larger areas in preference to more, smaller ones. Question 2) How few areas can I get away with, and still have a enough to keep critics quiet?
Thank for any help you can offer.