Exercise

Using t.test()

Manually calculating test statistics and transforming them with a CDF to get a p-value is a lot of effort to do every time you need to compare two sample means. The comparison of two sample means is called a t-test, and R has a t.test() function to accomplish it. This function provides some flexibility in how you perform the test.

As in the previous exercise, you'll explore the difference between the proportion of county-level votes for the Democratic candidate in 2012 and 2016.

sample_dem_data is available, and has columns diff, dem_percent_12, and dem_percent_16.

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Conduct a t-test on the sample differences (the diff column of sample_dem_data). Use an appropriate alternative hypothesis chosen from "two.sided", "less", and "greater".