Interesting findings on weights
Assume I have several variables to study from the sample, should we apply same or different weight? When will the weights be helpful to make the sample mean closer to the population mean? Are some weights more helpful than others depending on the nature of the variable? Our case is especially confusing, because different from a common study, the subject is not an individual, but a city! Most variables are city-based: city area, block size, etc. But each city has its own population size, and some variables are individual-based: like GDP per capita. GDP per capita is measured by the city, but its nature is an individual-level variable. We should treat them differently. Our data have offered a great opportunity to test these questions. We have a sample of 200 cities for which we have measured more than a hundred variables. These 200 samples were drawn from the 4231 global cities (named as the universe of cities ), which is the real population of the sample. We happen...