I have geometry feature class of states that I would like to build a choropleth map from by using the quantity of people in that state. However, the data of what people in what state is in seperate table with other attributes like first and last name and so on. Is there a way to count all of the, say, Washington State people from the seperate table and append a "population" attribute at the end of the geometry feature class' attribute table so that I may then use this newly derived "population" attribute to use for the choropleth map?
It sounds like you should be able to do a Frequency (Analysis) on the "state name" field of your separate table, and then join that to your states feature class on the state name field. See more about joining tables here.