Visualizing the difference

Before you start running hypothesis tests, it's a great idea to perform some exploratory data analysis; that is, calculating summary statistics and visualizing distributions.

Here, you'll look at the proportion of county-level votes for the Democratic candidate in 2012 and 2016, sample_dem_data. Since the counties are the same in both years, these samples are paired. The columns containing the samples are dem_percent_12 and dem_percent_16.

dem_votes_potus_12_16 is available as sample_dem_data. pandas and matplotlib.pyplot are loaded with their usual aliases.