Before creating a research question/thesis that relies on data that you are not collecting yourself, do some research to see if that data is available to you in a format that you can work with that includes all of your variables.
All federal agencies have web pages that may include not only useful reports and statistics, but also downloadable data sets. For example this page from the US Bureau of Labor. To find these pages do a search for the agency name in quotation marks followed by the phrase "data sets" like this: "US Department of Education" "data sets"