Analyzing Geographic Data with QGIS - Part 1

Today I'm writing this post to explain how it's possible to make geographic analysis and answer questions like: which is the richest area in my city? How many people do live in one neighborhood? You can do it combining shape files with an excel spreadsheet, let's understand it together... Then, we're gonna need one shape file and one excel spreadsheet. I'm from Brazil, and we do have a lot of open data from States and Cities.