When I was in Israel last week, we wanted to create a visualization that included band lines based on confidence intervals in the database.  In other words, our table contained two measures: value and confidence interval.

Allen Smithee had created some interesting looking Bollinger Bands before, so I started there.  I downloaded the workbook and noticed that while these look decent, they’re not perfect.  This is the initial view:

Looks pretty good.  But when you remove the lines for the upper and lower bands (or if you zoom in), you will see that the bands were made via reference bands for each discrete date, which makes them look like bars.  I suspect the lines for the upper and lower were included to hide the rough edges of the bars.

Here’s how he created the reference lines:

I don’t think this looks polished enough, so I took an alternative approach: area charts.