Today I was creating a scatter plot in Tableau using about 1.5 years of monthly data. All the data points looked like they correlated nicely except for the March 2013 data point. With March 2013 included in the trend line calculation, the scatter plot looked like this and the r-squared was 59.4%:
If the outlier was removed, the r-squared jumped to 98.1% and looked like this:
Notice that in the second graph, the March 2013 data point still shows up (but isn’t included in the trend line calculation). If you want to learn how that was done, simply watch this video to learn a couple of tricks.