I have a question about using census data to find population parameters. When you have undocumented migrants, there's an issue because your parameters can be inaccurate. An example is proportion of people whose first language is English. Is there a way to fix this problem? What would you call data from a census, apart from census data? The example of median income is not a "parameter" since you don't have all the information about the resident population. Also, I don't think it's a "statistic" because your sample size is more than 10% of the population, and your sampling frame doesn't include undocumented migrants.
I'm not sure what you mean by "because your parameters can be inaccurate." If you are asking if census estimates are inaccurate because of the presence of illegal immigrants in the United States, the US census attempts to count everyone, regardless of immigration status (illegal or not). Census data is just called "census data." I'm not sure what you mean either by "The example of median income is not a "parameter" since you don't have all the information about the resident population." By any chance are you doing a homework problem and trying to think out the answers to questions to which we aren't privy?
For more information about steps the US Census takes to account for criminal aliens see here: http://www.civilrights.org/census/messaging/immigrants.html