The proposal should establish one variable that's your dependent variable and three other independent variables that should cause that dependent variable. You must include a logical explanation for why each of the three independent variables should cause the dependent variable. This should be the bulk of the proposal. The independent variables should be very different from one another. Don't use both murder rates and assault rates, for example. Be creative! Avoid obvious connections (e.g. the birth rate causing the death rate; income causing consumption) and variables that are very similar (e.g. unemployment and average income). Note: average GDP is the same as average income. Don't make a state's or country's population a variable. That variable is there so you can adjust other variables for population. While population can be an appropriate dependent or independent variable, it's tricky to do right and best be avoided for the purposes of this course. Don't use the raw SAT scores as variables; those are too influenced by the participation rate. Use the adjusted score if you want to include SAT scores