What hypothesis and which test do I use?

Question

Which county had the highest median income between 2006 to 2010? The answer is Los Angeles. I have a real data, how do I turn this question to a hypothesis and which test do I use?

Answer 1

If your data includes all the population of all the counties and between 2006 and 2010 LA county had highest median income. There is no hypothesis to test. You can make that statement without qualification.

 

Question only arises if your median is based on a random sample of some people in each county and perhaps another county say Santa Clara was close enough, in that case if you want to assert that LA was higher than Santa Clara county you may need to setup hypothesis to test.