This is a follow-up to a question of what to do if you get a sample that is clearly not representative [What if your random sample is clearly not representative? ]
I have a population of 800 in 25 cities in 5 geographic areas. I want to avoid the possibility of getting a random sample that omits a geographic area. I expect no differences between geographic areas or cities.
What are the pros and cons of using stratified random sample (to assure that some people are sampled from each geographic area) as compared with a purely random sample. (Having a sample without people from each geographic area would be politically problematic.)